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

On the Verge of Magnetism. Joshua S. Alwood Mentor: G. R. Stewart University of Florida. Goals. Introduce magnetism Characterize non-Fermi liquid behavior Find the point when magnetism begins in the system U 2 (Ni x Co 1-x ) 2 In. Magnetism. Movement of charged particles

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

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  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. High T Low T Magnetic fields, H Paramagnetism Ferromagnetism Antiferromagnetism Magnetism

  16. Spin Orientation:High T, H = 0 • Paramagnet, Ferromagnet, Antiferromagnet • Non-magnetic

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

  18. Paramagnetism • Field dependent magnetic order H

  19. Magnetic order below TN H = 0 Antiferromagnetism

  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. Fit: c~co - A T a a = 0.46 3 K < T < 30 K Similar to known nFL U0.2Y0.8Pd3 a = 0.5 Magnetic Susceptibility

  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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