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Hall Coefficient of Chromium

Hall Coefficient of Chromium. Rafael Jaramillo Thomas Rosenbaum Lab P335 Project. BCC unit cell. Pure Cr. Elemental antiferromagnet below T neel =311 K Spin-density wave aligned along one of <100> crystal axes Spin-flip transition at T SF =123 K. image from Isaacs et Al.

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Hall Coefficient of Chromium

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  1. Hall Coefficient of Chromium Rafael Jaramillo Thomas Rosenbaum Lab P335 Project

  2. BCC unit cell Pure Cr • Elemental antiferromagnet below Tneel=311 K • Spin-density wave aligned along one of <100> crystal axes • Spin-flip transition at TSF=123 K image from Isaacs et Al.

  3. X-Ray Diffraction Results • Diffraction images of domains during spin-flip transition; E. D. Isaacs, et Al. (now at Argonne)

  4. Longitudinal Resistivity/ Hall Coefficient • Hall coefficient is more sensitive to the TNeel transition than the longitudinal resistivity (see Rosenbaum, et Al.) • Sensitivity of the Hall coefficient to the spin-flip transition is unknown • Objective: make detailed measurements of RH = (ne)-1 near TSF and Tneel • Correlate Hall data near transitions with diffraction data

  5. Experimental Setup H field • Field, temperature controlled by liquid He machine • Magnetic Property Measurement System (MPMS), by Quantum Design • Longitudinal resistance, Hall measurements taken with AC resistance bridge, recorded by MPMS software Hall voltage leads longitudinal voltage leads longitudinal current leads

  6. Next Steps • Magnetoresistance measurements as function of temperature • Take Hall data with a single-domain sample • Field-cool the Cr sample through TNeel with a strong enough H field, aligned along one of <100> directions • Need a two-axis field

  7. Selected References • Arrott and Werner, “First-Order Magnetic Phase Change in Chromium at 38.5oC”, Phys. Rev. Lett. 14: 1022-1024 (1965) • P.G. Evans, E.D. Isaacs, et Al., “X-ray microdiffraction images of antiferromagnetic domain evolution in chromium”, Science 295: 1042-1045 (2002) • E. Fawcett, “Spin-density-wave antiferromagnetism in chromium”, Rev. Mod. Phys. 60: 209-283 (1988) • A. Yeh, T.F. Rosenbaum, et Al. “Quantum phase transition in a common metal”, Nature 419: 459-462 (2002(

  8. MPMS Machine • Liquid He - cooled system; lowest temp 1.9 K (He4 boils at 4.2 K) • 5 Tesla (max) superconducting magnet • Sample space in magnet’s bore; maximum sample width is 9mm

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