MAGNETOVOLUME AND TETRAGONAL ELONGATION EFFECTS ON MAGNETIC PHASE-TRANSITIONS OF BODY-CENTERED TETRAGONAL FERH1-XPTX

Magnetic properties of FeRh1-xPtx system with body-centered cubic and body-centered tetragonal (bct) structures were studied by means of X-ray diffractometry, magnetometry and Mossbauer spectroscopy, and the phase diagram in a temperature-composition plane was determined. With substituting Pt for Rh, the axial ratio c/a was increased and the bct phase was stabilized. With increasing temperature, the bct alloys with 0.72<chi<0.81 underwent a first-order phase transition from the antiferromagnetic state to the ferromagnetic state, while the alloys with 0.3<chi<0.72 exhibited a first-order phase transition from the antiferromagnetic state to the paramagnetic state with a volume expansion and a tetragonal lattice distortion. The mechanism of those phase transitions was discussed in terms of the magneto-volume and the tetragonal elongation effect.