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Title: 27 February 2006


1
Neutron Scattering at the Ames
Laboratory 1947-2006
2
Beginning of Neutron Scattering at the Ames
Laboratory
The Neutron scattering program at the Ames
Laboratory was initiated by Frank H. Spedding,
founder and director of the Laboratory, and
Robert E. Rundle, former graduate student of
Linus Pauling, noted chemist and x-ray
crystallographer at the Laboratory. They were
among the first to realize the importance of
neutron scattering in determining magnetic
structures and light-atom (H and C) positions in
crystals.
F. Spedding, far left, at the first reactor
criticality experiment with Fermi and Compton in
Chicago, December 2, 1942.
R. Rundle, N. Belov, and F. Spedding, (l to r)
February of 1960. AIP Emilio Segre Visual
Archives
N. Bohr and F. Spedding. Iowa State University,
courtesy AIP Emilio Segre Visual Archives
In the late 1940s and 1950s, Spedding and Rundle
established a close collaboration in neutron
scattering between Ames Laboratory and Oak Ridge
National Laboratory which continues to this
day. The Ames Laboratory was established by the
Atomic Energy Commission (AEC) on the campus of
Iowa State College in 1947.
3
Beginning of Neutron Scattering at the Ames
Laboratory (cont.) Hydrides
Neutrons were immediately recognized as the
perfect probe to determine hydrogen positions in
crystals since, unlike x-rays, they are strongly
scattered by hydrogen. One of the earliest
studies of hydrides using neutrons (below right)
was performed by Robert Rundle in collaboration
with Cliff Shull and Ernie Wollan at the ORNL
Graphite Reactor.
Comparison of powder neutron-diffraction patterns
of ThH2 and ThD2. Acta. Cryst. 5, 22 (1952).
Ernie Wollan (left) and Cliff Shull at their
diffractometer at the ORNL Graphite Reactor
(1950).
R. E. Rundle, C. G. Shull, E. O. Wollan, "The
Crystal Structure of Thorium and Zirconium
Dihydrides by X-ray and Neutron Diffraction,"
Acta Cryst. 5, 22 (1952). A footnote in this
paper states, "The publication of the data and
conclusions in this paper have been delayed
considerably because of declassification
problems. All of the data were obtained and most
of the analysis performed during the middle of
1948 or earlier."
4
Beginning of Neutron Scattering at the Ames
Laboratory (cont.) Hydrides
Representative publications
"The Structure of Uranium Hydride and
Deuteride," R. E. Rundle, J. Am. Chem. Soc., 69,
1719 (1947). (This is an x-ray paper
demonstrating the lack of information provided by
x-rays on the hydrogen and deuterium
positions.) "The Hydrogen Positions in Uranium
Hydride by Neutron Diffraction," R. E. Rundle, J.
Am. Chem. Soc., 73, 4172 (1951). "The Crystal
Structure of Thorium and Zirconium Dihydrides by
X-ray and Neutron Diffraction," R. E. Rundle, C.
G. Shull, E. O. Wollan, Acta Cryst., 5, 22
(1952). "Deuterium Positions in Lanthanum
Deuteroxide by Neutron Diffraction," Masao Atoji
and Donald Williams, J. Chem. Phys., 31, 329
(1959).
5
Beginning of Neutron Scattering at the Ames
Laboratory (cont.) Carbides
Neutron-scattering techniques were used also to
accurately determine atomic positions in metal
carbides. Rundle initiated these measurements in
the early 1950s (left) and his work was continued
by Masao Atoji who traveled to Chicago and Oak
Ridge to use diffractometers at the Argonne and
Oak Ridge National Laboratories, respectively.
ThC2
UC2
Neutron diffraction pattern taken by C. G. Shull
at ORNL for ThC2. Below is shown the ThC2
distorted cell (solid line) versus the
previously-reported tetragonal structure. J.
Am. Chem. Soc., 73, 4777 (1951).
Neutron diffraction scan (above) for UC2 taken at
the CP5 reactor of Argonne National Laboratory
using the diffractometer operated by Dr. S Sidhu.
At right is the CaC2 structure (isostructural
to UC2) where the large circles are the metal
atoms and the small circles the carbon atoms. J.
Chem. Phys., 31, 332 (1959).
6
Beginning of Neutron Scattering at the Ames
Laboratory (cont.) Carbides
Representative publications
"The Structure of Thorium Dicarbide by X-Ray
and Neutron Diffraction," Elton B. Hunt and R. E.
Rundle, J. Am. Chem. Soc., 73, 4777 (1951).
"The Structures of Lanthanum Dicarbide and
Sesquicarbide by X-Ray and Neutron Diffraction,"
Masao Atoji, Karl Gschneidner, Jr., A. H. Daane,
R. E. Rundle and F. H. Spedding, J. Am. Chem.
Soc., 80, 1804 (1958). "Structures of Calcium
Dicarbide and Uranium Dicarbide by Neutron
Diffraction," Masao Atoji and Ronald C. Medrud,
J. Chem. Phys., 31, 332 (1959).
"Neutron-Diffraction Studies of La2C3, Ce2C3,
Pr2C3, and Tb2C3," Masao Atoji and Donald E.
Williams, J. Chem. Phys., 35, 1960 (1961).
"Neutron Diffraction Studies of CaC2, YC2, LaC2,
CeC2, TbC2, YbC2, LuC2 and UC2," Masao Atoji, J.
Chem. Phys., 35, 1950 (1961).
7
Beginning of Neutron Scattering at the Ames
Laboratory (cont.) Rare-Earths
Frank Spedding provided rare-earth samples to
Koehler and Wollan to initiate their pioneering
determination of paramagnetic cross sections
(below right) and magnetic structures of
rare-earth metals and alloys, using
neutron-scattering techniques at the ORNL
Graphite Reactor.
Wally Koehler at the HFIR HB1 Polarized
Spectrometer (1976).
Paramagnetic-scattering cross section per
rare-earth ion in Nd2O3 and Er2O3. Phys.Rev., 9,
1380 (1953).
"Slow Neutron Scattering Cross Sections for
Rare Earth Nuclides," W. C. Koehler and E. O.
Wollan, Phys. Rev., 91, 597 (1953).
"Paramagnetic Scattering of Neutrons by Rare
Earth Oxides," W. C. Koehler and E. O. Wollan,
Phys. Rev., 92, 1380 (1953).
8
The Ames Laboratory Research Reactor
Spedding asked for a research reactor to be
built at the Ames Laboratory in the early 1950s
AEC approves building the ALRR (CP5 type).
Funding approved in the late 1950s. Ground
breaking in fall of 1961. (photo at right, F.
Spedding, center) 1962-63 Reactor personnel
reactor operations (W. McCorkle) neutron
scattering (F. Spedding, A. Mackintosh, R.
Jacobson who joined the Chemistry division after
Rundles death) nuclear physics (W. Talbert).
17-Feb-1965 ALRR attains criticality, full power
12-July-1965.
1961
1961
1976
1962
9
Instrumentation at the Ames Laboratory Research
Reactor
Mitsubishi compound neutron instrument (1965) -
double-axis diffractometer "THUMB"

- triple-axis spectrometer
"FINGER" Ames Laboratory designed and
constructed triple-axis spectrometer TRIAX
(1970) Ames Laboratory built a second
triple-axis instrument for the National Bureau of
Standards reactor in 1972-73 (chosen over ORNL
and Grenoble designs)
from original Mitsubishi manuals
THUMB
TRIAX
FINGER
THUMB
TRIAX triple-axis neutron spectrometer designed
and constructed by the Ames Laboratory.
FINGER
Mitsubishi compound neutron diffractometer and
spectrometer. Photo at left from Iowa State
University Library/Special Collections Department
10
Instrumentation at the Ames Laboratory Research
Reactor (cont.)
White-beam neutron diffractometer technique
developed for determining single crystal
structures (1971). (below left) Polarized
diffractometer designed and constructed at the
Ames Laboratory. One of the first instruments
equipped with a superconducting magnet (1972).
(below right) Manual diffractometer (not
shown)- - training of students and postdocs -
single-crystal alignment and characterization,
powder pattern scans
polarized
Costa Stassis (above) and Jim Sayre transferring
liquid nitrogen into the superconducting magnet
mounted on the polarized diffractometer at the
ALRR.
Bob Jacobson, left, with Carl Quicksall, center,
and Cam Hubbard, right, at the white-beam
single-crystal diffractometer.
11
Instrumentation at the Ames Laboratory Research
Reactor (cont.)
TRISTAN was the first reactor-based on-line
isotope separation system in the world for the
study of short-lived radioactive nuclei produced
from neutron-bombarded 235U. (35 research
publications from 1966 to 1975)
TRISTAN
TRISTAN
Schematic layout of the on-line isotope separator
facility.
TRISTAN facility (1977).
The TRISTAN facility was moved to the HFBR at
Brookhaven National Laboratory in 1978 after the
shutdown of the ALRR.
12
Ames Laboratory Triple-Axis Spectrometer TRIAX
Installed at the ALRR in 1970 (first of two,
the 2nd was built for the National Bureau of
Standards). Moved to and reinstalled at the ORR
at ORNL in 1978. Completely modernized and
installed at the Missouri University Research
Reactor in 1995, using grants provided by the
National Science Foundation and the Department of
Energy.
TRIAX being disassembled for shipment to Oak
Ridge.
Original design drawing of TRIAX.
TRIAX in its present location at MURR at Missouri
University in Columbia, MO.
Chun Loong and Jerel Zarestky at TRIAX installed
at the ORR.
13
Quantum Solids
Quantum solids contain light elements whose
displacement from their equilibrium positions can
be comparable to their separation even at 0 K,
and their study presented extreme experimental
and theoretical challenges. Experiments at the
HFBR of BNL and at the ALRR of Ames Laboratory
established the validity of the self-consistent
phonon theory applied to these problems. This
method, with various modifications, is presently
used in the study of systems containing light
elements.
Dispersion curves of hcp 4He compared with the
theoretical predictions of Gillis, Koehler, and
Werthamer. Phys. Rev. A, 3, 1688 (1971).
Comparison of the experimental dispersion curves
with the self consistent theoretical
calculations of Horner. Phys. Rev. B, 17, 1130
(1978).
14
Quantum Solids (cont.)
Crystals for the experiments were grown in situ
under hydrostatic pressure in a special cryostat
(shown below) that could be disconnected from the
pressurizing apparatus to orient the crystal and
perform the experiments. Many of the techniques
pioneered at BNL and Ames Laboratory are being
used in present day cryostats for the study of
these systems.
Neutron "photograph" of crystal used for most of
the hcp-He measurements. Phys. Rev. A, 3, 1688
(1971).
Sunny Sinha adjusting the tilt of the He cryostat
on the Mitsubishi "FINGER" triple-axis at the
ALRR.
15
Quantum Solids (cont.)
Representative publications
"Phonon Dispersion Relations for hcp 4He at
Molar Volume of 16 cm3," R. A. Reese, S. K.
Sinha, T. O. Brun, and C. R. Tilford, Phys. Rev.
A, 3, 1688 (1971). "Phonon Spectra of fcc
4He," J. G. Traylor, C. Stassis, R. A. Reese, and
S. K. Sinha, Proc. Fifth Symposium on Neutron
Inelastic Scattering, (IAEA), 129 (1972).
"Lattice Dynamics of fcc 4He," C. Stassis, G. R.
Kline, W. A. Kamitakahara, and S. K. Sinha, Phys.
Rev. B, 17, 1130 (1978). "Neutron Diffraction
Measurement of the Debye-Waller Factor of Solid
hcp 4He," C. Stassis, D. Khatamian, and G. R.
Kline, Solid State Commun. 25, 531 (1978).
16
First Determination of Induced Magnetic Form
Factor of an Actinide
The study of the magnetic properties of actinides
did not advance as fast as that of the rare-earth
compounds because of the difficulty in handling
these materials. To the best of our knowledge,
the first induced magnetic form factor of an
actinide (below right) was measured using the ANL
polarized instrument (photo at left) installed at
the ALRR by Gerry Lander in 1968 during the
extended shut-down of the ANL CP-5 reactor.
?-U
ANL polarized
Experimental magnetic form factor for a-uranium
metal compared to ltjogt and combined results of
uranium in compounds (hatched region). Phys. Rev.
B, 17, 308 (1978).
ANL polarized diffractometer installed at the
ALRR (1968 to 1970). Iowa State University
Library/Special Collections Department
"Induced magnetization density in ?-uranium,"
R. Maglic, G.H. Lander, M.H. Mueller and R. Kleb,
Phys. Rev. B 17, 308 (1978).
17
Field Induced Magnetization in Itinerant Cr
Field-induced magnetic form factors provide
direct measurement of the magnetization at the
Fermi level of a metal and its separation into
spin and orbital contributions. The
induced-moment form factor of Cr, a typical
itinerant metal, was found to be atomic-like
(right), quite a surprising result at that time.
Subsequently, band theoretical calculations using
the relativistic augmented-plane-wave (RAPW)
method confirmed the experimental results.
Angular dependence of the induced-moment magnetic
scattering amplitude of Cr, compared with 3d-spin
and 3d-orbital free-atom form factors. The
3d-spin curve is the magnetic form factor of
chromium in the ordered state (Moon, Koehler and
Trego). Inset temperature dependence of the
(110) magnetic scattering amplitude. Phys. Rev.
Lett., 31, 1498 (1973).
"Polarized-Neutron Study of the Field-Induced
Magnetic Moment in Chromium," C. Stassis, G. R.
Kline, and S. K. Sinha, Phys. Rev. Lett., 31,
1498 (1973). "Field-Induced-Magnetic-Moment
Form Factor of Metallic Chromium," C. Stassis, G.
R. Kline, and S. K. Sinha, Phys. Rev. B, 11, 2171
(1975). "Induced magnetic form factor of
chromium," K. H. Oh, B. N. Harmon, S. H. Liu and
S. K. Sinha, Phys. Rev. B, 14 1283 (1976).
18
First Experimental Demonstration of an
Incommensurate Magnetic Structure
The study of the magnetic structure of Er, on
samples of higher purity than those used at ORNL,
demonstrated the incommensurate nature of the
structure. In fact, the number of harmonics
detected was only limited by the background
(figure below shows the intensities of satellites
up to 17th order). This and similar experiments
paved the way for the present-day theoretical
understanding of the origin of the magnetic
structures of rare-earth metals and compounds.
Integrated reflectivities of the higher-order
harmonics of the c-axis moment vs. temperature.
Phys. Rev. B, 10, 1020 (1974).
"Neutron Diffraction Study of the Magnetic
Structure of Erbium," M. Habenschuss, C. Stassis,
S. K. Sinha, H. W. Deckman, and F. H. Spedding,
Phys. Rev. B, 10, 1020 (1974).
19
Move to the Oak Ridge Research Reactor of ORNL
The ALRR was shut down for the last time on
31-Dec-1977. By Feb-1978 three instruments
had been disassembled and then shipped to ORNL
for installation at the Oak Ridge Research
Reactor (ORR). - TRIAX triple-axis
spectrometer - polarized diffractometer -
the THUMB, modified as a stand-alone two-axis
diffractometer - also shipped was ancillary
equipment computers, cryostats, magnets,
furnaces, pumps, etc.
polarized
TRIAX
Rollie Struss, Gary Kline and Jerel Zarestky
disassemble TRIAX for shipment to Oak Ridge
(above two photos).
Costa Stassis with equipment ready to be shipped
to the ORR.
20
Move to the Oak Ridge Research Reactor of ORNL
(cont.)
All three instruments were brought on-line at the
ORR (fall of 1978 - spring 1979). Four Ames
Laboratory staff, postdocs and grad students
moved to Oak Ridge.
ORR containment building
ORR reactor floor before AL installations
TRIAX
polarized
Chun Loong and Jerel Zarestky at the polarized
diffractometer (left photo) and the TRIAX
spectrometer (right photo) installed at the ORR.
21
Field-Induced Magnetization in Paramagnetic Metals
Polarized neutron scattering techniques were used
to measure the conduction electron field-induced
magnetization in paramagnetic metals. These
results and those obtained by the ORNL neutron
scattering group provided a strict test of band
theoretical calculations of the electronic
properties of metallic solids (see figs. below).
It was demonstrated that signals as small as 10-3
- 10-4 ( in magnetic fields of 60-120 KG) could
be measured and separated from other
contributions such as diamagnetic scattering and
nuclear polarization.
Comparison of the experimental results on Zr with
calculations (triangles) assuming a 65 spin-35
orbital distribution of the induced moment. J.
Magn. Magn. Mater., 14, 303 (1979).
Comparison of the measured form factor of Lu with
atomic and relativistic augmented-plane-wave
(RAPW) calculations of the spin form factor.
Solid State Commun., 23, 159 (1977).
22
Field-Induced Magnetization in Paramagnetic
Metals (cont.)
Representative publications
"Polarized-Neutron Study of the Induced
Magnetic Moment in TmSb," G.H. Lander, T.O. Brun
and O. Vogt, Phys. Rev. B, 7, 1988 (1973).
"Field-Induced Magnetic Form Factor of
Lutetium," C. Stassis, G. R. Kline, C.-K. Loong,
and B. N. Harmon, Solid State Commun., 23, 159
(1977). "Induced magnetization density in
?-uranium," R. Maglic, G.H. Lander, M.H. Mueller
and R. Kleb, Phys. Rev. B, 17, 308-311
(1978). "Field-Induced Magnetic Form Factor of
g -Ce," C. Stassis, C.-K. Loong, G. R. Kline, O.
D. McMasters, and K. A. Gschneidner, Jr., J.
Appl. Phys., 49, 2113 (1978). "Polarized
Neutron Studies of the Field Induced
Magnetization in Paramagnetic Metals and Their
Interpretation," C. Stassis, Nukleonika, 24, 765
(1979). "Field Induced Magnetic Form Factor of
Zr," C. Stassis, G. Kline, B. N. Harmon, R. M.
Moon, and W. C. Koehler, J. Magn. Magn. Mater.,
14, 303 (1979).
23
High Temperature Studies
We were the first to initiate the study of the
lattice dynamics of high temperature and
metastable phases of metals by growing in situ
(on the sample table of a triple-axis
spectrometer) single crystals of these phases.
Their dispersion curves are rich in phonon
anomalies and their interpretation led to the
establishment of frozen phonon calculations as a
powerful first-principles technique for revealing
the electronic origin of these anomalies.
Selected examples are shown below.
fcc La
bcc Zr
Giant low temperature Kohn-anomaly in the T???
branch of of fcc-La. (right) Phys. Rev. B, 31,
6298 (1985).
Dispersion curves of bcc Zr (left) showing
pronounced dip at 2/3??? indicating an
instability toward the ?-phase. Phys. Rev.
Lett., 41, 1726 (1978).
?-Fe
bcc Zr bcc La
Large elastic anisotropy is implied by the
anomalously low T2??0 branches for bcc Zr and
La. (right) Solid State Commun., 52, 9 (1984).
Dispersion curves of ?-Fe (fcc). (right) Note
the positive dispersion in the T2??0 branch.
Phys. Rev. B, 35, 4500 (1987).
24
High Temperature Studies (cont.)
The in situ crystal growth technique was also
used to study the lattice dynamics of difficult
to handle and reactive materials. To this date,
this is the only direct information available
regarding the lattice dynamics of these metals.
Examples are shown in the figures below.
bcc Ba Phys. Rev. B, 32, 666 (1985)
bcc Sr Phys. Rev. B, 32, 8372 (1985)
fcc Ca Phys. Rev. B, 27, 3303 (1983)
bcc Cs Phys. Rev. B, 34, 5890 (1986)
25
High Temperature Studies (cont.)
Representative publications
"Temperature Dependence of the c-Axis Phonon
Dispersion Curves of hcp Zr," C. Stassis, J. L.
Zarestky, and B. N. Harmon, Solid State Commun.,
26, 161 (1978). "Temperature Dependence of the
Normal Vibrational Modes of hcp Zr," C. Stassis,
J. L. Zarestky, D. Arch, O. D. McMasters, and B.
N. Harmon, Phys. Rev. B, 18, 2632 (1978).
"Lattice Dynamics of bcc Zirconium," C. Stassis,
J. L. Zarestky, and N. Wakabayashi, Phys. Rev.
Lett., 41, 1726 (1978). "Lattice Dynamics of
hcp Ti," C. Stassis, D. Arch, B. N. Harmon, and
N. Wakabayashi, Phys. Rev. B, 19, 181, (1979).
"Lattice and Spin Dynamics of g-Ce," C. Stassis,
T. Gould, O. D. McMasters, K. A. Gschneidner,
Jr., and R. M. Nicklow, Phys. Rev. B, 19, 5746
(1979). "On the Lattice Dynamics of hcp
Hafnium," C. Stassis, D. Arch, J. L. Zarestky, O.
D. McMasters, and B. N. Harmon, Solid State
Commun., 35, 259 (1980). "Lattice Dynamics of
hcp Hf," C. Stassis, D. Arch. O. D. McMasters,
and B. N. Harmon, Phys. Rev. B, 24, 730 (1981).
"Origin of the Zone-Center 001 LO-Phonon
Anomaly in Superconducting hcp Transition
Metals," S. H. Liu, C. Stassis, and K.-M. Ho,
Phys. Rev. B, 24, 5093 (1981). "Addendum to the
Lattice Dynamics of g-Ce," C. Stassis, C.-K.
Loong, O. D. McMasters, and R. M. Nicklow, Phys.
Rev. B, 25, 6485 (1982). "Phonon Dispersion
Curves of fcc La," C. Stassis, C.-K. Loong, and
J. L. Zarestky, Phys. Rev. B, 26, 5426 (1982).
"Lattice Dynamics of fcc Ca," C. Stassis, J. L.
Zarestky, D. Misemer, H. L. Skriver, B. N.
Harmon, and R. M. Nicklow, Phys. Rev. B, 27, 3303
(1983). "Temperature Dependence of the
Vibrational Modes of Molybdenum," J. L. Zarestky,
C. Stassis, B. N. Harmon, K.-M. Ho, and C.L. Fu,
Phys. Rev. B, 28, 697 (1983). "Study of the
T1110 Phonon Dispersion Curves of bcc La and
Zr," C. Stassis and J. L. Zarestky, Solid State
Commun., 52, 9 (1984). "Polarized Neutron Study
of the Paramagnetic Scattering from ?-Fe," P.
Böni, G. Shirane, J. P. Wicksted, and C. Stassis,
Phys. Rev. B, 31, 4597 (1985). "Low Temperature
Kohn Anomaly in Metastable fcc Lanthanum," C.
Stassis, G. S. Smith, B. N. Harmon, K.-M. Ho, and
Y. Chen, Solid State Commun., 53, 773 (1985).
"Lattice Dynamics of the Metastable fcc Phase of
Lanthanum," C. Stassis, G. S. Smith, B. N.
Harmon, K.-M. Ho, and Y. Chen, Phys. Rev. B, 31,
6298 (1985). "Anomalous Low Temperature Lattice
Dynamics of fcc Lanthanum," X.-W. Wang, Y. Chen,
K.-M. Ho, C. Stassis, B. N. Harmon, and W. Weber,
Physica, 135B, 477 (1985). "Phonon Dispersion
Curves of bcc Ba," J. Mizuki, Y. Chen, K.-M. Ho,
and C. Stassis, Phys. Rev. B, 32, 666 (1985).
"Lattice Dynamics of bcc Sr," J. Mizuki and C.
Stassis, Phys. Rev. B, 32, 8372 (1985).
"Anomalous Lattice Dynamics of fcc Lanthanum," X.
W. Wang, B. N. Harmon, Y. Chen, K.-M. Ho, C.
Stassis, and W. Weber, Phys. Rev. B, 33, 3851
(1986). "Anomalously Low 100 Longitudinal
Phonon Branch in Ba The Role of the
d-Hybridization," Y. Chen, K.-M. Ho, B. N.
Harmon, and C. Stassis, Phys. Rev. B, 33, 3684
(1986). "Lattice Dynamics of bcc Cs," J. Mizuki
and C. Stassis, Phys. Rev. B, 34, 5890 (1986).
"Lattice Dynamics of ?-Fe," J. L. Zarestky and
C. Stassis, Phys. Rev. B, 35, 4500 (1987).
"Phonon Dispersion of bcc-La," F. Güthoff, W.
Petry, C. Stassis, A. Heiming, B. Hennion, C.
Herzig, J. Trampenau, Phys. Rev. B, 47, 2563
(1993). "Inelastic Neutron Scattering of g-Iron
and the Determination of the Elastic Constants by
Lattice Dynamics," C. Stassis, in High-Pressure
Science and Technology - 1993, Ed. by S. C.
Schmidt, J. W. Shaner, G. A. Samara, and M. Ross
(AIP Press), Vol. 1, p. 955 (1994).
26
Furnace for High Temperature Studies
The versatile high-temperature vacuum furnace
design developed at the Ames Laboratory was
adopted by W. Petry at the Institute
Laue-Langevin for the construction of a more
advanced version for use at the ILL reactor. At
present, sophisticated furnaces of this type are
in use in practically all neutron scattering
centers.
Photos at left, (l to r) the 1200 C furnace
assembled, with outer vacuum can removed and with
heat shields removed. A 1600º C version of this
furnace was also designed, built, and used in
neutron experiments.
The 1200º C furnace mounted on the sample table
of the TRIAX at the ORR (left) and on the HB1
triple-axis spectrometer at the HFIR (right).
27
Mixed-Valence and Heavy-Fermion Superconductors
Mixed-valence and heavy-fermion systems are of
continuing interest because of their fascinating
physical properties. The polarized neutron
study of CeSn3 was the first direct demonstration
of a change as a function of temperature of the
electronic character of the wave functions at the
Fermi level in a mixed-valence compound (left
fig.). In the case of the heavy-fermion
superconductors, on the other hand, no change in
the form factor was observed below TC, which is
still a challenging theoretical problem. (right
two figs.)
Induced-moment form factor of UPt3 (left) and
UBe13 (right) in the normal low-temperature
state. The solid line represents the fit to the
5f form factor of U3. Phys. Rev. B, 34, 4382
(1986).
Magnetic form factor data on CeSn3 obtained with
two different samples (open and solid symbols) at
four temperatures with the field parallel to the
110 direction (circles) and 100 direction
(triangles). J. Appl. Phys., 50, 2091 (1979).
28
Mixed-Valence and Heavy-Fermion Superconductors
(cont.)
Representative publications
"Temperature Dependence of the Field Induced
Magnetic Form Factor of CeSn3," C. Stassis, C.-K.
Loong, O. D. McMasters, and R. M. Moon, J. Appl.
Phys., 50, 2091 (1979). "Polarized Neutron
Study of the Paramagnetic Scattering from
CeCu2Si2," C. Stassis, B. Batlogg, J. P. Remeika,
J. D. Axe, G. Shirane, and Y. J. Uemura, Phys.
Rev. B, 33, 1680 (1986). "Induced-Moment
Magnetic Form Factor of the Heavy Fermion
Superconductors UPt3, UBe13, and CeCu2Si2," C.
Stassis, J. Arthur, C. F. Majkrzak, J. D. Axe, B.
Battlog, J. Remeika, Z. Fisk, J. L. Smith, and A.
S. Edelstein, Phys. Rev. B, 34, 4382 (1986).
29
Amorphous Semiconductors
These materials are of considerable interest
because of their use in solar-energy devices. We
performed the first experimental determination of
the vibrational density of states of amorphous
silicon (a-Si) and related materials. (left fig.)
Left (a) Experimental vibrational density of
states of a-Si (crosses) compared with theory
(open circles). This spectrum is to be contrasted
with (b) that obtained on poly crystalline
samples (crosses experimental points, solid
line theory of Weber). Phys. Rev. B, 36, 6539
(1987).
Improved theories better describe the
experimental results (above). Solid line
molecular dynamics dashed line Monte Carlo. The
points are neutron-scattering data. Phys. Rev.
B, 38, 10499 (1988).
30
Amorphous Semiconductors (cont.)
Representative publications
"Phonon density of states of amorphous-silicon,"
H. R. Shanks, W. A. Kamitakahara, J. F.
McClelland, C. Carlone, J. Non-crys. Sol., 59,
197 (1983). "Measurement of Phonon Densities
of States for Pure and Hydrogenated Amorphous
Silicon," W. A. Kamitakahara, H. R. Shanks, J. F.
Mcclelland, U. Buchenau, F. Gompf, L.
Pintschovius, Phys. Rev. Lett., 52, 644
(1984). "Vibrational-spectrum of amorphous
silicon Experiment and computer-simulation," W.
A. Kamitakahara, C. M. Soukoulis, H. R. Shanks,
U. Buchenau, G. S. Grest, Phys. Rev. B, 36, 6539
(1987). "Vibrational Localization in
Amorphous-Silicon," R. Biswas, A. M. Bouchard, W.
A. Kamitakahara, G. S. Grest, C. M. Soukoulis,
Phys. Rev. Lett., 60, 2280 (1988).
"Neutron-Scattering from Low-Frequency
Excitations in Amorphous-Germanium," U. Buchenau,
M. Prager, W. A. Kamitakahara, H. R. Shanks, N.
Nucker, Europhys. Lett., 6, 695 (1988).
"Vibrational properties of amorphous
silicon-germanium alloys and superlattices," A.
M. Bouchard, R. Biswas, W. A. Kamitakahara, G. S.
Grest, C. M. Soukoulis, Phys. Rev. B, 38, 10499
(1988). "Dynamics of Amorphous Semiconductors
Experiment and Computer-Simulation," W. A.
Kamitakahara, R. Biswas, A. M. Bouchard, and F.
Gompf, Physica B, 156, 213 (1989).
31
Graphite Intercalation Compounds (GICs)
GICs are fascinating materials produced by the
reaction of metals or acidic molecular species
with graphite, resulting in high-conductivity
nearly 2D metals, some of which have important
practical applications (Li-graphite is commonly
used in present day Li batteries). We performed
the first systematic neutron scattering study of
these systems. In particular, we observed unusual
phonon properties in some of these compounds
(KC24, below-left) and established a
quantitative relation between metallic properties
(charge transfer) and C-C nearest -neighbor
distances (below, right).
Decrease of C-C bond length vs. charge transfer
per C atom, or vs. intercalation time, for
graphite intercalated with D2SO4 (circles), H2SO4
(triangle) and SbCl5 (shaded horizontal bar at
time 40 hr). The crosses and solid line
represent the current calculations. Phys. Rev.
Lett., 58, 1528 (1987).
Transverse 100 modes of KC24. The
mode-splitting in the acoustical branch is
possibly due to alkali order-disorder
transformation. Phys. Rev. B, 26, 5919 (1982).
32
Graphite Intercalation Compounds (cont.)
Representative publications
"Neutron-scattering investigation of
layer-bending modes in alkali-metal graphite
intercalation compounds," H. Zabel, W. A.
Kamitakahara, R. M. Nicklow, Phys. Rev. B, 26,
5919 (1982). "Effect of In-Plane Density on
the Structural and Elastic Properties of Graphite
Intercalation Compounds," K. C. Woo, W. A.
Kamitakahara, D. P. Divincenzo, D. S. Robinson,
H. Mertwoy, J. W. Milliken, J. E. Fischer, Phys.
Rev. Lett., 50, 182 (1983). "Experimental
phase diagram of lithium-intercalated graphite,"
K. C. Woo, H. Mertwoy, J. E. Fischer, W. A.
Kamitakahara, D. S. Robinson, Phys. Rev. B, 27,
7831 (1983). "Neutron spectroscopy of phonons
in stage-1 rubidium-intercalated graphite," W. A.
Kamitakahara, N. Wada, S. A. Solin, L. M.
Seaverson, Phys. Rev B, 28, 3457 (1983). "C-C
Bond Distance and Charge-transfer in D2SO4 -
Graphite Compounds," W. A. Kamitakahara, J. L.
Zarestky, P.C. Eklund, Synthetic Metals, 12
(1-2), 301 (1985). "In-plane intercalate
dynamics in alkali-metal graphite intercalation
compounds," W. A. Kamitakahara, H. Zabel, Phys.
Rev. B, 32, 7817 (1985). "Dynamics of 2D
Alkali Domains in Graphite Intercalation
Compounds," H. Zabel, M. Suzuki, D. A. Neumann,
S. E. Hardcastle, A. Magerl, and W. A.
Kamitakahara, Synthetic Metals, 12, 105
(1985). "Zone-center phonon frequencies for
graphite and graphite intercalation compounds
Charge-transfer and intercalate-coupling
effects," C. T. Chan, K. -M. Ho, W. A.
Kamitakahara, Phys. Rev. B, 36, 3499 (1987).
"Charge-Transfer Effects in Graphite
Intercalates Ab Initio Calculations and
Neutron-Diffraction Experiment ," C. T. Chan, W.
A. Kamitakahara, K. -M. Ho, P. C. Eklund, Phys.
Rev. Lett., 58, 1528 (1987).
33
HB1A Ames Laboratory Spectrometer at the HFIR
HB1A fixed-initial-energy triple-axis
spectrometer Ames Laboratory (Jerel Zarestky,
Costa Stassis) in collaboration with the ORNL
neutron scattering group (Joe Cable, Ralph Moon)
designed, built, and installed the HB1A
instrument at HFIR in 1990. After the upgrade
of the HFIR (right), an upgraded version (left)
was reinstalled at HFIR and became available to
outside users in April of 2003. (Between Apr-2003
and Dec-2005, 150 experiments involving 54
investigators were performed on HB1A.)
HFIR with new guide hall and cooling towers.
From left to right David Vaknin, Rob McQueeney,
Costa Stassis and Jerel Zarestky at the HB1A
spectrometer installed at HFIR.
34
HB1A Ames Laboratory Spectrometer at the HFIR
(cont.)
HB1A features intense beam at fixed Ei 14.6
meV low l/2 contam. I l/210-4 I l low
gamma, fast neutron background ideal
configuration for low energy excitations at high
temperatures good resolution (lt1 meV), high
intensity and low background for elastic
measurements
HB1A after 2001-2 HFIR upgrade larger HB1 beam
tube divergence gave a factor of 2-3 in increased
flux improved M2 shielding evacuated flight
path M1 to M2 10-15 flux increase precision
circular rail system for analyzer/detector axis
new triple-axis computer operating system SpICE
Future HB1A Upgrades new analyzer/detector
shield motorized slits before sample position
for reflectivity measurements evacuated and
shielded flight path between M2 and sample
neutron CCD camera for crystal characterizations
and sample alignment
circular rail system (from above)
Schematic layout of HB1A.
35
High-TC Superconductors and Related Materials
The neutron scattering effort of the Ames
Laboratory in this area was started using the
facilities at the HFBR of BNL (at the time of the
discovery of high-TC materials, both the ORR and
the HFIR were down). The experiments at the
HFBR, lead by S. K. Sinha of Exxon, established
correctly the antiferromagnetic structure of the
high-TC parent compounds for the first time.
(fig. at left La2CuO4-y figs. at right
Sr2CuO2Cl2)
Temperature dependence of the integrated
intensity of the (½,½,0) magnetic
neutron-diffraction peak for a single crystal
specimen of Sr2CuO2Cl2. The solid curve is a fit
of the quantity A(1-T/TN)2b to the data, where TN
251 K and b 0.30. Phys. Rev. B, 41, 1926
(1990).
Fits of the Sr2CuO2Cl2 experimental data (solid
circles) to the Cu2 magnetic form factor (solid
curve) and the results of band theoretical
calculations (diamonds). J. Appl. Phys., 67, 4524
(1990).
Top figure intensity vs scattering angle 2? for
neutron powder scans of the (100) peak region at
15 K and at room temperature. Bottom figure
(100) peak intensity vs temperature. The solid
line is a spin ½ magnetization curve for TN 220
K, calculated from molecular field theory. J.
Appl. Phys., 63, 4015 (1988).
36
High-TC Superconductors and Related Materials
(cont.)
Representative publications
"Antiferromagnetism in the High-TC Related
Compounds," S. K. Sinha, D. E. Moncton, D. C.
Johnston, D. Vaknin, G. Shirane, and C. Stassis,
J. Appl. Phys., 63, 4015 (1988). "Neutron
Scattering Studies of Antiferromagnetism in the
High-TC Compounds," S. K. Sinha, D. Vaknin, M. S.
Alvarez, A. J. Jacobson, J. Newsam, J. T.
Lewandowski, D. C. Johnston, C. Stassis, J. M.
Tranquada, T. Freltoft, H. Moudden, A. I.
Goldman, P. Zolliker, D. E. Cox, and G. Shirane,
in Proceedings of the International Conference on
Neutron Scattering, Grenoble, 12-15 July 1988,
edited by C. Vettier (North Holland, Amsterdam,
1988). "Antiferro-magnetism in Sr2CuO2Cl2," D.
Vaknin, S. K. Sinha, C. Stassis, L. L. Miller,
and D. C. Johnston, Phys. Rev. B, 41, 1926
(1990). "Antiferromagnetic Form Factor of
Sr2Cu02Cl2," X. L. Wang, L. L. Miller, J. Ye, C.
Stassis, B. N. Harmon, D. C. Johnston, A. J.
Schultz, and C.-K. Loong, J. Appl. Phys., 67,
4524 (1990).
37
High-TC Superconductors and Related Materials
(cont.) RNi2B2C
The RNi2B2C system (R rare-earth) is a
fascinating family of intermetallics comprising
some compounds in which superconductivity
coexists with magnetic order (R Ho, Er) and
others with relatively high-TCs (R Y, Lu).
The correct magnetic structure of the Ho and Er
variants was determined for the first time by
measurements on single crystals prepared at the
Ames Laboratory. Particularly important is the
observation of the pair-breaking in the Ho
compound (fig. at left) and the detection of the
modulation with q 0.553 a in Er (fig. at
right).
ErNi2B2C T 7 K
HoNi2B2C
Temperature dependence of (a) the first- (open
ellipse) and third-order (filled ellipse)
satellites associated with the modulation wave
vector K1 0.915 c (b) the K2 0.585 a
magnetic satellite and (c) the upper critical
field Hc2 Phys. Rev. B, 50, 9668 (1994).
Typical single-crystal scan along a showing the
(000) and (200)- first order satellites
associated with the modulation wave vector qa
0.553 a. Phys. Rev. B, 51, 678 (1995).
38
High-TC Superconductors and Related Materials
(cont.) RNi2B2C
In superconducting RNi2B2C (R Y, Lu) the
acoustic and lowest optic branches of the phonon
dispersion curves are of the same symmetry, and
therefore, cannot cross, which is a rare
situation (fig. at left). Explaining the
behavior of the phonon modes of these branches in
the center of the zone, as well as their observed
temperature dependence and change in shape below
TC presents a challenge to present-day theories.
The changes in the frequencies of these modes,
after crossing TC, is so spectacular that
originally they were thought to be associated
with a new excitation (figs. at right).
Phonon dispersion of the two low-lying ?4
acoustic (A) and optic (O) branches measured, at
300 K, along the ?00 direction for LuNi2B2C
(left) and YNi2B2C (right). Phys. Rev. B, 57,
7916 (1998).
Neutron groups for LuNi2B2C (TC 16.6 K) at two
Qs as a function of temperature. Physica C, 318,
127 (1999).
The ?4 ?,0,0 dispersion curves of YNi2B2C at
620 and 150 K. Filled (open) circles denote data
obtained around the (107) ((108)) reciprocal
lattice point. Physica C, 318, 127 (1999).
39
High-TC Superconductors and Related Materials
(cont.) RNi2B2C
Representative publications
"Magnetic Pair Breaking in HoNi2B2," A. I.
Goldman, C. Stassis, P. C. Canfield, J. L.
Zarestky, P. Dervenagas, B. K. Cho, D. C.
Johnston, and B. Sternlieb, Phys. Rev. B, 50,
9668 (1994). "Magnetic Structure of ErNi2B2C,"
J. L. Zarestky, C. Stassis, A. I. Goldman, P. C.
Canfield, P. Dervenagas, B. K. Cho, and D.C.
Johnston, Phys. Rev. B (Rapid Commun.), 51, 678
(1995). "Magnetic Structure of DyNi2B2C," P.
Dervenagas, J. L. Zarestky, C. Stassis, A. I.
Goldman, P.C. Canfield, and B. K. Cho, Physica B,
212, 1 (1995). "Magnetic Structures in RNi2B2C
(RHo,Er) Superconductors," C. Stassis, A. I.
Goldman, P. Dervenagas, J. L. Zarestky, P. C.
Canfield, B. K. Cho, D. C. Johnston, and B.
Sternlieb, in Neutron Scattering in Materials
Science II, Materials Research Society Symposium
Proceedings, 376, 559 (1995). "Incommensurate
Modulations in the Magnetic Structures of the
Antiferromagnetic Superconductor HoNi2B2C - a
High-Resolution Neutron Powder Diffraction
Study," T. Vogt, C. Stassis, A. Goldman, P.
Canfield, and B. Cho, Physica B, 215, 159
(1995). "Observations of Oscillatory Magnetic
Order in the Antiferromagnetic Superconductor
HoNi2B2C," T. Vogt, A. Goldman, B. Sternlieb, and
C. Stassis, Phys. Rev. Lett., 75, 2628 (1995).
"Soft Phonons in Superconducting LuNi2BxC," P.
Dervenagas, M. Bullock, J. L. Zarestky, P.
Canfield, B. K. Cho, B. N. Harmon, A. I. Goldman,
C. Stassis, Phys. Rev. B, 52, R9839 (1995).
"Superconducting and Normal State Magnetic
Properties of RNi2B2C Single Crystals,"F. Borsa,
B. K. Cho, P. C. Canfield, P. Dervenagas, A. I.
Goldman, D. C. Johnston, B. N. Harmon, L. L.
Miller, C. Stassis, B. J. Suh, D. R. Torgeson, M.
Xu, J. L. Zarestky, M. F. Hundley, R. Movshovitz,
J. D. Thompson, A. V. Chubukov, B. Sternlieb,
Chinese J. Phys., 34, 397 (1996). "The Magnetic
Structure of GdNi2B2C by Resonant and
Non-Resonant X-ray Scattering," C. Detlefs, A. I.
Goldman, J. P. Hill, D. Gibbs, C. Stassis, P. C.
Canfield, B. K. Cho, Phys. Rev. B, 53, 6355
(1996). "Magnetic Structure of TbNi2B2C," P.
Dervenagas, J. L. Zarestky, C. Stassis, A. I.
Goldman, P. Canfield, B. K. Cho, Phys. Rev. B,
53, 8506 (1996). "Incommensurate
Antiferromagnetism in the Intermetallic
Superconductor HoNi2B2C," J. P. Hill, C. Detlefs,
B. Sternlieb, D. Gibbs, A. I. Goldman, C.
Stassis, B. K. Cho, P. Canfield, Phys. Rev. B,
53, 3487 (1996). "Observation of a Square
Flux-Line Lattice in the Magnetic Superconductor
ErNi2B2C," U. Yaron, P. L. Gammel, A. P. Ramirez,
D. A. Huse, D. J. Bishop, A. I. Goldman, C.
Stassis, P. C. Canfield, K. Mortensen, and M. R.
Eskildsen, Nature, 382, 236 (1996). "Phonon
Mode Coupling in Superconducting LuNi2B2C," C.
Stassis, M. Bullock, J. L. Zarestky, P. Canfield,
A. Goldman, G. Shirane, S. Shapiro, Phys. Rev. B,
55, R8678 (1997). "Single Crystal Neutron
Diffraction Study of the Magnetic Structure of
TmNi2B2C," B. Sternlieb, C. Stassis, A. Goldman,
P. Canfield, S. Shapiro, J. Appl. Phys., 81, 49
(1997). "Neutron and X-ray Scattering Studies
of RNi2B2C (R rare-earth) Single Crystals," C.
Stassis, A. I. Goldman, J. Alloys Comp., 250, 603
(1997). "Magnetoelastic Tetragomel to
Orthorhombic Distortion in ErNi2B2C," C. Detlefs,
A. Islam, T. Gu, A. Goldman, C. Stassis, P.
Canfield, Phys. Rev. B, 56, 7843 (1997). "Low
Energy Phonon Excitations in Superconducting
RENi2B2C (RELu,Y)," M. Bullock, J. Zaretsky, C.
Stassis, A. Goldman, P. Canfield, Z. Honda, G.
Shirane, S.M. Shapiro, Phys. Rev. B, 57, 7916
(1998). "Inelastic Neutron Scattering Studies
of the Low-Energy Phonon Excitations in the
RENi2B2C Superconductors," M. Bullock, C.
Stassis, J. L. Zarestky, A. I. Goldman, P.
Canfield, G. Shirane, S. Shapiro, Physica B,
241-243, 798 (1998). "Anomalous Phonons Below
Tc in Superconducting RNi2B2C (RLu,Y)," C.
Stassis, J. L. Zarestky, A. Goldman, P. Canfield,
G. Shirane, S. Shapiro, Physica C, 317-318, 127
(1999). "Phonon Profiles in Superconducting
YNi2B2C and LuNi2B2C," J. L. Zarestky, C.
Stassis, A. Goldman, P. Canfield, G. Shirane, S.
Shapiro, Phys. Rev. B, 60, Nov 1 issue (1999).
"Phonon-Phonon Interactions in (Lu,Y)Ni2B2C," J.
L. Zarestky, C. Stassis, A. Goldman, P. Canfield,
G. Shirane, S. M. Shapiro, J. Phys. Chem. Sol.,
63, 811 (2002).
40
High-TC Superconductors and Related Materials
(cont.) Cu6 and Cu18 Clusters in BaCuO2x
Neutron-diffraction techniques were used to
determine the complex magnetic structure of
BaCuO2x (90 spins per unit cell) and identify
ring-like Cu6 and sphere-like Cu18 clusters
(shown below left), and lone Cu spins as
components of that structure. At low
temperatures, the ring and sphere clusters were
found to have ferromagnetic ground states with
saturated spins 3 and 9, respectively. At
temperatures below TN 15 K, however, the Cu6
rings exhibit antiferromagnetic intercluster
order whereas the Cu18 spheres remain
paramagnetic down to 50 mK.
Perspective representation of the two types of
Cu/O clusters in the bcc unit cell of BaCuO2x.
The Cu18 spheres are at the bc positions and the
Cu6 rings are at the eight 1/4(111) equivalent
positions. Lone Cu spins (not shown) are located
along principal directions adjacent to the
spheres. Phys. Rev. B, 57, 465 (1998)
Unpolarized neutron scattering intensity versus
scattering angle of BaCuO2x at 4.2K and 90K.
Science, 264, 402 (1994)
41
High-TC Superconductors and Related Materials
(cont.) Cu6 and Cu18 Clusters in BaCuO2x
Representative publications
"Antiferromagnetic Ordering and Paramagnetic
Behavior of Ferromagnetic Cu6 and Cu18 Clusters
in BaCuO2x," Z.-R. Wang, X.-L. Wang, J. A.
Fernandez-Baca, D. C. Johnston, and D. Vaknin
Science, 264, 402 (1994). "Static
Magnetization and AC Susceptibility Measurements
of the Copper-Oxygen Cluster Compound BaCuO2x,"
Z. R. Wang, D. C. Johnston, L. L. Miller, and D.
Vaknin Phys. Rev. B, 52, 7384 (1995). "Neutron
Diffraction Study of the Magnetic Ordering of
BaCuO2x," X.-L. Wang, J. A. Fernandez-Baca, Z.
R. Wang, D. Vaknin, and D. Johnston Physica B,
213214, 97 (1995). "Magnetic Neutron
Diffraction from the Magnetic Clusters in Single
Crystal BaCuO2x," D. Vaknin, J. P. Koster, Z.
W. Wang, J. L. Zarestky, J. Fernandez-Baca, and
D. C. Johnston. Phys. Rev. B, 57, 465 (1998).
42
Thin Films and Interfaces
Neutron-reflectivity techniques, were developed
and applied to the study of interfacial
properties of soft matter materials, polymers,
lipid and protein membranes, crystal growth and
ionic distributions under Langmuir monolayers.
For the first time, neutron and x-ray
reflectivities, in this particular case, on a
protein monolayer adsorbed to an aqueous surface,
were analyzed with one general model (figs.
below).
Normalized x-ray (a,b) and neutron (c,d)
reflectivities of protein/lipid surface layers on
H2O and D2O. The momentum-transfer ranges
indicate the complementary nature of the neutron
and x-ray techniques.
D. Vaknin, K. Kjaer, H. Ringsdorf, R.
Blankenburg, M. Piepenstock, A. Diederich and M.
Lösche. Langmuir, 9, 1171 (1993).
43
Materials of Technological Importance Hydrogen in
Metals
With the energy crisis of the early 1980s, metals
absorbing hydrogen became of considerable
scientific interest because of their potential
use for hydrogen storage. The results of some
early neutron scattering studies performed at the
ORR are given below.
Comparison of observed and calculated structure
factors of YD0.176 (left figure, Phys. Rev. B,
23, 624 (1981)) and Sc and ScD0.33 (right two
figures, Phys. Rev. B, 27, 7013 (1983) ) at room
temperature showing, in each case, good agreement
over a wide range of sin??? and indicating
precision in deuterium positions.
44
Materials of Technological Importance
(cont.) Hydrogen in Metals
Representative publications
"Crystal structure of YD1.96 and YH1.98 by
neutron diffraction," D. Khatamian, W. A.
Kamitakahara, R. G. Barnes and D. T. Peterson,
Phys. Rev. B, 21, 2622 (1980). "Location of
deuterim in ?-yttrium," D. Khatamian, C. Stassis,
and B. J. Beaudry, Phys. Rev. B, 23, 624
(1981). "Distribution of Hydrogen Vibrations
in LaH2.28 and LaH2.99," W. A. Kamitakahara and
R. K. Crawford, Solid State Commun., 41, 843
(1982). "Location of deuterim in ?-scandium,"
C. K. Saw, B. J. Beaudry and C. Stassis, Phys.
Rev. B, 27, 7013 (1983). "Neutron diffraction
study of ScD1.8," D. S. Robinson, J.L. Zarestky,
C. Stassis and D. T. Peterson, Phys. Rev. B, 34,
7374 (1986).
45
Materials of Technological Importance
(cont.) Shape Memory and Magnetostrictive
Materials
Many compounds and alloys of technological
importance are complex materials that are
difficult to prepare and study experimentally.
Because of their applications, martensitic,
shape-memory, and Heusler alloys, as well as
materials exhibiting giant magnetostriction are
of particular importance and were studied
extensively. Many of these studies were conducted
in collaboration with Lluis Mañosa of the
University Barcelona. As shown in the examples
here, some of the alloys exhibit spectacular
phonon softening. The T2110 phonon branch of
the shape-memory alloy Ni2MnGa shows anomalous
soft-mode behavior. (left) Fe-Ga (below and
right) exhibits the largest shift in frequencies
observed in a ferromagnet by alloying
substitutionally with non-magnetic atoms. The
softening of the phonons of the T2110 branch is
particularly dramatic and explains the giant
magnetostriction observed in these alloys.
The soft-mode behavior of the T2110 branch of
the phonon dispersion curves for two slightly
different compositions of Ni2MnGa, at selected
temperatures above the martensitic transition.
Phys. Rev. B, 64, 024305 (2001).
The T2110 branch (above left) and the elastic
constants (above right) for five compositions of
Fe-Ga. Phys. Rev. B, 72, 180408(R) (2005).
46
Materials of Technological Importance
(cont.) Shape Memory and Magnetostrictive
Materials
Representative publications
"Lattice-dynamical study of the premartensitic
state of the Cu-Al-Be alloys," Ll. Mañosa, J. L.
Zarestky, T. Lograsso, D. W. Delaney, and C.
Stassis, Phys. Rev. B, 48, 15708 (1993).
"Elastic constants of bcc Cu-Al-Ni alloys," Ll.
Mañosa, M. Jurado, A. Planes, J. L. Zarestky, T.
Lograsso, and C. Stassis, Phys. Rev. B, 49, 9969
(1994). "An Experimental Study of the Coupling
Between the Order-Disorder Transition and the
Martensitic Transfer Motion in Cu-Al-Be Shape
Memory Alloys," M. Jurado, Ll. Mañosa, A. Planes,
and C. Stassis, J. de Physique IV, C2, 165
(1995). "Atomic Order and Martensitic
Transformation in Cu-Al-Be Shape-Memory Alloy,"
M. Jurado, Ll. Mañosa, A. Gonzàlez-Comas, C.
Stassis, A. Planes, J. de Physique, 5, C8-973
(1995). "A Comparative Study of the Post-Quench
Behavior of Cu- Al-Be and Cu-Zn-Al Shape Memory
Alloys," Ll. Mañosa, M. Jurado, A.
Gonzàlez-Comas, E. Obrad , A. Planes, J. L.
Zarestky, C. Stassis, R. Romero, A. Somoza, M.
Morin, Acta Mater., 46, 1045 (1998). "Low-lying
phonon dispersion curves of DO3Cu3Al(Be)," Ll.
Mañosa, J. L. Zarestky, M. Bullock, C. Stassis,
Phys. Rev. B 59, 9239 (1999). "Phonon softening
in Ni-Mn-Ga alloys," Ll. Mañosa, Antoni Planes, J
.L. Zarestky, T. Lograsso, D. L. Schlagel, C.
Stassis, " Phys. Rev. B, 64, 024305 (2001).
"Elastic constants of Ni-Mn-Ga magnetic shape
memory alloys, M. Stipcich, Ll. Mañosa, A.
Planes, M. Morin, J. L. Zarestky, T. Lograsso, C.
Stassis, Phys. Rev.B 70, 054115 (2004).
"Compositional variation of the phonon dispersion
curves of bcc Fe-Ga alloys," J. L. Zarestky, V.O.
Garlea, T. A Lograsso, D. L. Schlagel and C.
Stassis, Phys. Rev. B, 72, 180408(R) (2005).
"Lattice dynamics and phonon softening in
Ni-Mn-Al Heusler alloys," Xavier Moya, Lluis
Mañosa, Antoni Planes, Thorsten Krenke, Mehmet
Acet, V. O. Garlea, T. A. Lograsso, D. L.
Schlagel and J. L. Zarestky, Phys. Rev. B, 73,
064303 (2006).
47
Materials of Technological Importance
(cont.) Li-ion Rechargeable Battery Materials
Lithium-orthophosphates LiMPO4 (M Mn, Fe, Co,
Ni) have attracted considerable interest in
recent years because of their relatively high
lithium ionic-conductivity which may be utilized
in rechargeable battery technology, and their
intriguing magnetic properties, in particular,
their strong magneto-electric effect. Of
particular importance is LiFePO4, which has
already been tested as a high-potential cathode
in secondary Li-ion rechargeable batteries
Nature Mater. 4, 254 (2005). Neutron
diffraction and dynamics studies reveal the
nature of the magnetic phases in these systems.
In particular, a novel commensurate-incommensurate
phase transition was identified in LiNiPO4. (see
figs. below)
Magnetic phase diagram of LiNiPO4 determined by
neutron-diffraction studies. The sketch at left
depicts the antiferromagnetic ground state at low
temperatures and the incommensurate structure at
intermediate temperatures. The commensurate to
incommensurate phase transition is first order.
Phys. Rev. Lett., 92, 20720 (2004).
Neutron-diffraction scans along (0,k,0) direction
showing the evolution with changing temperature
of the incommensurate magnetic structure in
LiNiPO4. Phys. Rev. Lett., 92, 20720 (2004).
48
Materials of Technological Importance
(cont.) Li-ion Rechargeable Battery Materials
Representative publications
"Weakly (x0) and Randomly (x0.03) Coupled
Ising Antiferromagnetic Planes in LixFe1-xNiPO4
compounds," D. Vaknin, J. L. Zarestky, J. E.
Ostenson, B. Chakoumakos, A. Goñi, P.J. Pagliuso,
T. Rojo, and G. E. Barberis. Phys. Rev. B, 60,
1100 (1999). "Antiferromagnetism in
?-Li3Fe2(PO4)3," J. L. Zarestky, D. Vaknin, B.
C. Chakoumakos, T. Rojo, A. Goñi, and G. E.
Barberis J. Magn. Magn. Mater., 234, 401
(2001). "Weakly Coupled Antiferromagnetic
Planes in Single-Crystal LiCoPO4," D. Vaknin,
J.L. Zaretsky, L.L. Miller, J.-P. Rivera and H.
Schmid Phys. Rev. B, 65, 224414 (2002).
"Commensurate-Incommensurate Magnetic Phase
Transition in Magnetoelectric Single Crystal
LiNiPO4," D. Vaknin, J. L. Zarestky, J.-P.
Rivera, and H. Schmid, Phys. Rev. Lett., 92,
20720 (2004). "Antiferromagnetism in
Magnetoelectric Single Crystals LiCoPO4 and
LiNiPO4," D. Vaknin, J. L. Zarestky, J.-P.
Rivera, and H. Schmid, Magnetoelectgric
Interactions Phenomena in Crystals, Eds. M.
Fiebig, V. Eremenko, and I. E. Chupis, Kluwer,
London, 203 (2004). "Spin-waves in
antiferromagnetic single crystal LiFePO4," J. Li,
V. O. Garlea, J. L. Zarestky, D. Vaknin Phys.
Rev. B, 73, 024410 (2006).
49
Ames Laboratory Neutron Scattering Contribution
to the Periodic Table
Phonon dispersion curves and magnetic form
factors of elemental materials measured by the
Ames Laboratory neutron scattering group.
phonon dispersion curves
magnetic form factor
both
selected phases, i.e. ? -Fe, bcc-Zr, ?-Ce).
50
Publication and Citation statistics
51
Past students, postdocs and scientists who spent
formative years in neutron scattering at the
Ames Laboratory
Harold Smith (ORNL) Masao Atoji (ANL) Allan
Mackintosh (Tech U. Lyngby, Dir. Danish
AEC/RISO) Sunil Sinha (ANL, Exxon, UCSB) Torben
Brun (ANL, LANL) Yuji Ito (Tokyo U.) Junji
Sakurai (Hiroshima U.) Thomas Prevender (Sandia
National Laboratory) Charles Tilford
(NBS/NIST) Nobu Wakabayashi (ORNL, Keio U.
Tokyo) Lewis Muhlenstein (MURR) Allan Reese
(Union Carbide) Gerry Lander (ANL, JRC Karlsruhe,
Dir. E.U.s ITU) Cam Hubbard (ORNL-HTML) Nancy
Chesser (Directed Technologies Inc.)
Joe Traylor (Buena Vista U.) Bill Kamitakahara
(DOE, NIST) Harry Deckman (Exon) Michael Pechan
(Miami U. OH) Jerel Zarestky (Ames
Laboratory) Chun Loong (ANL) David Arch
(Honeywell) Djamshid Khatamian (U. Toronto, AECL
Chalk River) Jean-Louis Staudenmann (BNL-NSLS,
NIST-ATP) Cheng Saw (Celanese, LLNL) Greg Smith
(Exon, LANL, ORNL) Jun Mizuki (NEC,
JASRI-SPring8) Xun-Li Wang (ORNL-SNS) Max Bullock
(Ratheon) Ovidiu Garlea (ORNL)
52
Ames Laboratory Neutron Scattering Support
Most of the accomplishments of the Ames
Laboratory neutron scattering group would not
have been possible without the technical support
provided by engineering services and the samples
prepared for us by the materials preparation
scientists. Rollie Struss and his group
designed and constructed the TRIAX triple-axis
spectrometer and the polarized neutron
diffractometer, one of the first equipped with a
superconducting magnet. A duplicate of TRIAX was
constructed for the National Bureau of Standards
(NIST) and installed at their reactor in
Gaithersburg, MD. TRIAX has recently been
upgraded and modernized and is still in operation
at the Missouri University Research
Reactor in Columbia. Harold Skank and his group
designed the electronics and computer control
system for TRIAX, the polarized neutron
diffractometer and later HB1A. Harold designed
the first fast-flipping system for polarized
neutrons, which is essential for measuring
signals as small as 10-4. Frank Spedding and
his group provided the samples used by W. Koehler
for the determination of the magnetic structures
of rare-earth metals and compounds. Karl
Gschneidner, Jr., Bernie Beaudry and Dale
McMasters provided us with the samples needed for
our studies of rare-earth metals and compounds.
Dale McMasters developed a variety of techniques
that we used for growing in situ single-crystals
of the high-temperature and metastable phases of
materials. Gary Kline was the first Ames
Laboratory staff member to join the group. He
assisted Dr. Stassis with the installation of the
polarized neutron diffractometer at the ALRR. He
was also the first to move to Oak Ridge to assist
in the installation of the three Ames Laboratory
instruments at the ORR. Ken Kliewer, who
provided administrative support of the group
during the trying times of the ALRR shutdown and
arranging the move to the ORR at Oak Ridge
National Laboratory. Tom Lograsso and the
Materials Preparation Center provided
single-crystals of the martensitic alloys and
giant magnetostrictive materials (Fe-Ga). Paul
Canfields group provided the single-crystals for
our studies of RNi2B2s.
53
Ames Laboratory Neutron Scattering Support
(cont.)
Sample growth and preparation Frank Spedding Karl
Gschneidner, Jr. Bernard Beaudry Dale
McMasters Frederick Schmidt Thomas Lograsso Paul
Canfield
Instrument and sample environment design Roland
Struss Philip Ward James Sayre Clarence
McCullough Michael Harper Terrance Herrman
Electronics and computer control Harold
Skank William Thomas John Erickson Clare
Tweedt John Hjortshoj Software design Thomas
Pintor Elaine Notice Dennis Jensen James
Flatten Edward Hendrickson
54
Theoretical Contributions
Traditionally, the Ames Laboratory
neutron-scattering scientists aimed to obtain a
fundamental understanding of experimental results
and collaborated closely with the theorists at
Ames as well as those at other laboratories and
universities. Allan Mackintosh and
collaborators made important early contributions
to our understanding of the electronic origin of
rare-earth magnetic structures and positron
annihilation in these metals. Scientists of
our group made seminal contributions to the
microscopic theory of lattice dynamics, magnetic
scattering of neutrons, and neutron diffraction
by perfect crystals. Bruce Harmon, Kai-Ming Ho
and their students of the Ames Laboratory theory
group closely collaborated with
neutron-scattering scientists on many
investigations. These studies established for
the first time that the wave functions obtained
in the RAPW approximation are adequate to
evaluate the induced magnetization in
paramagnetic metals. This collaboration also
established the power of first-principle
frozen-phonon calculations to explain phonon
anomalies in elements, martensitic alloys, and
other systems.
55
Theoretical contributions (cont.)
Representative publications
A. R. Mackintosh, "Magnetic Ordering and the
Electronic Structure of Rare-Earth Metals," Phys.
Rev. Lett., 9, 90 (1962). A. R. Mackintosh,
"Magnetoelastic Effects in Longitudinal Fields,"
Phys. Rev., 131, 2420 (1963). D. R. Gustafson,
A. R. Mackintosh, and D. J. Zaffarano, "Positron
Annihilation in Liquid and Solid Mercury," Phys.
Rev., 130, 1455 (1963). A. R. Mackintosh, L.
E. Spanel, and R. C. Young, "Magnetoresistance
and Fermi Surface Topology of Thallium," Phys.
Rev. Lett., 10, 434 (1963). D. R. Gustafson
and A. R. Mackintosh, "Positron Annihilation in
Rare-Earth Metals," J. Phys. Chem. Solids, 25,
389 (1964). H. Bjerrum Møller and A. R.
Mackintosh, "Observation of Resonant Lattice
Modes by Inelastic Neutron Scattering," Phys.
Rev. Lett., 15, 623 (1965). R. J. Kearney, A.
R. Mackintosh, and R. C Young, "Open-Orbit
Resonances in Tin," Phys. Rev., 140, A1671
(1965). R. W. William, T. L. Loucks, and A. R.
Mackintosh, "Positron Annihilation and the
Electronic Structure of Rare-Earth Metals," Phys.
Rev. Lett., 16, 168 (1966). W. C. Koehler and
R. M. Moon, and A. L. Trego and A. R. Mackintosh,
"Antiferromagnetism in Chromium Alloys. I.
Neutron Diffraction," Phys. Rev., 151 405
(1966). R. W. Williams and A. R. Mackintosh,
"Electronic Structure of Rare-Earth Metals. II.
Positron Annihilation," Phys. Rev., 168, 679
(1968). A. L Trego and A. R. Mackintosh,
"Antiferromagnetism in Chromium Alloys. II.
Transport Properties," Phys. Rev., 166, 495
(1968). S. K. Sinha, "Lattice Dynamics of
Copper," Phys. Rev. B, 143, 422 (1966). S. K.
Sinha and G. Venkataraman, "Effect of Nuclear
Spin Correlations on the Scattering of Neutrons
by Molecules," Phys. Rev., 149, 1 (1966). S.
K. Sinha, "Electron-Phonon Interaction and Phonon
Dispersion Relations Using the Augmented-Plane-Wav
e Method," Phys. Rev., 169, 477 (1968). S. K.
Sinha, "Derivation of the Shell Model of Lattice
Dynamics and its Relation to the Theory of the
Dielectric Constant," Phys. Rev,. 177, 1256
(1969). S. K. Sinha, S. H. Liu, L. D.
Muhlestein, and N. Wakabayashi,
"Neutron-Scattering Study of Magnons and
Paramagnons in a Chromium-Manganese Alloy," Phys.
Rev. Lett., 23, 311 (1969). S. K. Sinha, T. O.
Brun, L. D. Muhlestein, and J. Sakurai, "Lattice
Dynamics of Yttrium at 295 K," Phys. Rev. B, 1,
2430 (1970). R. P. Gupta and S. K. Sinha,
"Exchange Enhanced Generalized Susceptibility
Functions for Paramagnetic Chromium Including
Band Structure Effects," J. App. Phys., 41, 915
(1970). R. P. Gupta and S. K. Sinha,
"Wave-Number-Dependent Susceptibility Function
for Paramagnetic Chromium," Phys. Rev. B, 3, 2401
(1971). S. K. Sinha, D. L. Price, and R. P.
Gupta, "Generalized Screening Model for Lattice
Dynamics," Phys. Rev. Lett., 26, 1324 (1971).
S. H. Liu, R. P. Gupta, and S. K. Sinha,
"Generalized Susceptibility Function for Rare
Earths and Thorium and Their Alloys," Phys. Rev.
B, 4, 1100 (1971). R. E. De Wames and S. K.
Sinha, "Possibility of Guided-Neutron-Wave
Propagation in Thin Films," Phys. Rev., 7, 917
(1973). N. Wakabayashi and S. K. Sinha,
"Microscopic
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