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Magnetoelastic behavior of rare earth based
intermetallics in high magnetic fields up to 33 T
M. Doerra, M. Rotterb , J. Brooksc,d, E.
Jobiliongd, A. Lindbaumb, R. Vasicd, and M.
Loewenhaupta a Institute of Solid State Physics
(IFP), TU Dresden, D-01062 Dresden, GERMANY b
Institute of Physical Chemistry, University
Vienna, Währingerstr. 42, A-1090 Vienna,
AUSTRIA c Department of Physics, Florida State
University, Tallahassee, FL 32306-5350, USA d
National High Magnetic Field Laboratory (NHMFL),
Tallahassee, FL 32310-3704, USA
Magnetostriction in high magnetic fields
Rare earth intermetallics ... RCu2

• Experimental methods
• X-ray or neutron diffraction (spontaneous
  effects, Hconst., sensitivity 10-5)
• Extensometers (using strain gauges, spontaneous
  and field induced effects, successfully tested
  in pused fields, sensitivityf 10-6)
• Interferometry (spontaneous effects H0,
  sensitivity 10-7)
• Capacitive dilatometry (spontaneous and field
  induced effects, sensitivity 10-9 - but
  practically only 10-7)

4f R Ce Pr Nd Pm
Sm Eu Gd Tb Dy Ho Er Tm Yb
Magnetostriction Phase diagram (easy
direction)
The capacitive miniature-dilatometer ....
measures thermal expansion at Hconst. and
magnetostriction at Tconst. with a resolution of
10-7 (in supercond. magnets) .... uses a tilted
plate capacitor made from Ag .... has small
dimensions diameter d22mm, height h40mm 1
M.Rotter et al., Rev.Sci.Instrum. 69 (1998)
2742. Magnets The dilatometer was
successfully used in ... .... a superconducting
17 T-magnet (Oxford Instruments) with a 4He-gas
flow cryostat or a 3He insert (T 0.3...300 K).
.... water-cooled resistive magnets with 4He
bath cryostats
Miniature dilatometer 1 (a,p....shielding
electrodes, b,o....capacitor plates, c...screen,
d...distance piece, e...sample, f...sapphire
rings, q,r....holder)
NHMFL
33T-BITTER-magnet NHMFL Tallahassee
Sample stick with the capacitive miniature
dilatometer (Ag-cell, right) (installation at
NHMFL)
23T-BITTER-magnet GHMFL Grenoble
Magnetostriction measurements on RCu2 were
performed up to the highest available steady
magnetic fields. They show the transitions
between different magnetically ordered phases
clearly. Together with magnetization measurements
the allow to construct the magnetic phase
diagrams. Especially, the influence of magnetic
transitions on the crystalline structures via
magnetoelastic interaction can be studied. It may
result in lattice distortions, giant
magnetostrictive effects GMS 3 and symmetry
changes or low dimensional lattice expansion.
Model of magnetostriction
Summary
Sample stick with the capacitive miniature
dilatometer (Ag-cell, right) (installation at
GHMFL)

• The RCu2 compounds magnetostriction result from
  ...
• the single ion crystal field (CEF) contribution
  and
• the two ion exchange interaction.
• The mean field Monte Carlo simulation program
  McPhase (www.mcphase.de) allows to model the
  magnetostriction.
• The elastic constants important for
  applications - can be calculated.
• 2 M.Rotter, M. Doerr, M. Loewenhaupt, P.
  Svoboda J. Appl. Phys. 91 (2002) 8885.
• 3 M. Doerr, A. Lindbaum, M. Rotter Adv. Phys.
  54 (2005) 1.

• Magnetostriction measurements are a powefull tool
  to study the magnetoelastic interactions and
  magnetic phase transitions.
• The magnetoelastic behavior can be calculated
  using a theoretical model which takes into
  account the crystal field striction as well as
  the exchange striction.
• Magnetostrictive measurements in resistive.
  water cooled high field magnets give good
  results. The resolution is still limited to 10-6
  by mechanical vibrations.

Noise levels in BITTER-magnets
We acknowledge support by the Austrian Science
Foundation (FWF) within the projects P16957 and
P17226 and by the Deutsche Forschungsgemeinschaft
(DFG) within the Sonderforschungsbereich 463. A
portion of this work was performed at the
National High Magnetic Field Laboratory, which is
supported by NSF Cooperative Agreement No.
DMR-0084173, by the State of Florida, and by the
DOE.