Joshua S. Alwood

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On the Verge of Magnetism

• Joshua S. Alwood
• Mentor G. R. Stewart
• University of Florida

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Goals

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

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Magnetism

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

A B
B
A
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Spin Magnetic Moment
-
e
Electron at rest
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
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Spin Magnetic Moment
m
_
m
?
e
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Magnetism

• High T
• Low T
• Magnetic fields, H

• Paramagnetism
• Ferromagnetism
• Antiferromagnetism

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Spin OrientationHigh T, H 0

• Paramagnet, Ferromagnet, Antiferromagnet
• Non-magnetic

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Ferromagnetism

• Spontaneous magnetic order
• T dependent
• H 0

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Paramagnetism
H

• Field dependent magnetic order

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Antiferromagnetism

• Magnetic order below TN
• H 0

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Research

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

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Research

• Heavy Fermions
• Non-Fermi liquids

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Motives

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

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Fermi Liquid Theory

• T 0
• C / T constant
• c constant

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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

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My Project

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

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Sample Preparation

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

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Sample Preparation

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

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Magnetic Susceptibility

• Measures extent of magnetism
• Defined as c M / H

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Magnetic Susceptibility
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Magnetic Susceptibility
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Magnetic Susceptibility
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Magnetic Susceptibility
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Magnetic Susceptibility
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Magnetic Susceptibility
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Magnetic Susceptibility
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U2Ni1.3Co0.7In

• Last paramagnetic compound
• Peak at TN 0 K ?????

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Magnetic Susceptibility
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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

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Conclusions

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

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Thank You!

• NSF, UF Physics
• G. R. Stewart
• J. S. Kim and R. Pietri