1ST-ORDER MAGNETIC PHASE-TRANSITIONS OBSERVED IN BCT FERH-PT, PD SYSTEMS

FeRh1-xPtx and FeRh1-yPdy systems with body-centered tetragonal (bct) structure were prepared and the magnetic phase diagrams were determined in a temperature-composition plane. The axial ratio c/a increases with substituting Pt or Pd for Rh. The alloys with 0.25 less-than-or-equal-to x less-than-or-equal-to 0.75 or 0.3 < y less-than-or-equal-to 0.5 undergo a first-order transition from antiferromagnetic to paramagnetic behaviours by heating above room temperature. The transition is deeply related to the nature of itinerant electron system with anisotropically distorted lattice. The magnetic behaviours were interpreted in terms of magneto-volume effect and tetragonal elongation effect in the framework of the spin fluctuation theory.