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Joshua S. Alwood

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Joshua S. Alwood. Mentor: G. R. Stewart. University of Florida. On the Verge of Magnetism ... Find the point when magnetism begins in the system U2(NixCo1-x)2In ... – PowerPoint PPT presentation

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Title: Joshua S. Alwood


1
On the Verge of Magnetism
  • Joshua S. Alwood
  • Mentor G. R. Stewart
  • University of Florida

2
Goals
  • Introduce magnetism
  • Characterize non-Fermi liquid behavior
  • Find the point when magnetism begins in the
    system U2(NixCo1-x)2In

3
Magnetism
  • Movement of charged particles
  • Vector sum of spin magnetic moments

A B
B
A
4
Spin Magnetic Moment
-
e
Electron at rest
5
Spin Magnetic Moment
6
Spin Magnetic Moment
7
Spin Magnetic Moment
8
Spin Magnetic Moment
9
Spin Magnetic Moment
10
Spin Magnetic Moment
11
Spin Magnetic Moment
12
Spin Magnetic Moment
13
Spin Magnetic Moment
14
Spin Magnetic Moment
m
_
m
?
e
15
Magnetism
  • High T
  • Low T
  • Magnetic fields, H
  • Paramagnetism
  • Ferromagnetism
  • Antiferromagnetism

16
Spin OrientationHigh T, H 0
  • Paramagnet, Ferromagnet, Antiferromagnet
  • Non-magnetic

17
Ferromagnetism
  • Spontaneous magnetic order
  • T dependent
  • H 0

18
Paramagnetism
H
  • Field dependent magnetic order

19
Antiferromagnetism
  • Magnetic order below TN
  • H 0

20
Research
  • G. R. Stewart
  • Low temperature, 0.4 - 10 K
  • Specific heat, C
  • Magnetic Susceptibility, c
  • Resistivity, r

21
Research
  • Heavy Fermions
  • Non-Fermi liquids

22
Motives
  • H. Nakotte, 1994
  • U2Co2In paramagnet
  • U2Ni2In antiferromagnet
  • Non-Fermi liquid behavior

23
Fermi Liquid Theory
  • T 0
  • C / T constant
  • c constant

24
Non-Fermi Liquid Theory (nFL)
  • Andraka (UF) and Tsvelik, Seaman, et al., 1991
  • Magnetic transition at T 0 K
  • Temperature dependence of C, c, and r at low T
  • Explicit forms of C, r
  • No general c predictions

25
My Project
  • Prepare high quality samples
  • Use SQUID to measure c
  • Seek magnetic transition

26
Sample Preparation
  • U2(NixCo1-x)2In, where x
    is nickel concentration
  • High purity elements
  • Stoichiometry

27
Sample Preparation
  • Arc melting
  • X-ray diffraction (performed by Material
    Science)

28
Magnetic Susceptibility
  • Measures extent of magnetism
  • Defined as c M / H

29
Magnetic Susceptibility
30
Magnetic Susceptibility
31
Magnetic Susceptibility
32
Magnetic Susceptibility
33
Magnetic Susceptibility
34
Magnetic Susceptibility
35
Magnetic Susceptibility
36
U2Ni1.3Co0.7In
  • Last paramagnetic compound
  • Peak at TN 0 K ?????

37
Magnetic Susceptibility
38
Magnetic Susceptibility
  • Fit c co - A T a
  • a 0.46
  • 3 K lt T lt 30 K
  • Similar to known nFL U0.2Y0.8Pd3
  • a 0.5

39
Conclusions
  • U2Ni1.3Co0.7In could be nFL
  • Further work U2Ni1.4Co0.6In Measure c at
    lower T Measure C, r

40
Thank You!
  • NSF, UF Physics
  • G. R. Stewart
  • J. S. Kim and R. Pietri
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