Structure-dependent ferromagnetism in Au4 V studied under high pressure

Academic Article

Abstract

  • At ambient pressure, ordered Au4 V is metallic and displays ferromagnetism at TC =45 K. The electrical resistivity has been measured as a function of temperature from 1 K to 300 K and as a function of pressure up to 30 GPa using various high-pressure devices. A kink, which is associated with the reduction of scattering due to the onset of ferromagnetic order, is seen in the electrical resistance as a function of temperature. With applied pressure, this kink is found to broaden and increase in temperature at a rate of approximately 2.7 K GPa. Above ∼18 GPa, the broadening of the kink prohibits accurate determination of TC; however, upon reducing the pressure, no signatures of ferromagnetism were evident in the electrical resistivity. Both energy-dispersive (P≤61 GPa) and angle-dispersive (P≤27 GPa) x-ray diffraction measurements at room temperature show a gradual transition from the body-centered-tetragonal phase of Au4 V to a disordered face-centered-cubic structure. This transition is irreversible and continuous, and the data have been fit to a Birch-Murnaghan equation of state. In order to investigate the origin of the magnetic interactions in Au4 V, we have also measured the electrical resistivity of Au1-x Vx alloys and determined their Kondo temperatures TK for x<1%. The pressure dependence of TK for x=0.5% was measured up to 2.8 GPa, for which the Kondo temperature increases at a rate of d TK dP=6.5 K GPa. Using the volume dependence of the exchange interaction between magnetic vanadium ions, we find that the pressure-induced increase of the Curie temperature in Au4 V can be explained by an increase in the exchange interaction parameter and the number of magnetic nearest neighbors. © 2006 The American Physical Society.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Jackson DD; Jeffries JR; Qiu W; Griffith JD; McCall S; Aracne C; Fluss M; Maple MB; Weir ST; Vohra YK
  • Volume

  • 74
  • Issue

  • 17