Magnetic phase transitions in Fe72Pt28 Invar compound studied by high-pressure X-ray magnetic circular dichroism and X-ray diffraction

X-ray magnetic circular dichroism (XMCD) measurements have been performed u nder high pressure and used to study the disordered Fe72Pt28 Invar alloy. T he well-known high spin to low spin state transition is observed at 4 GPa. In addition, XMCD evidences a second transition to the nonmagnetic phase at high pressure in the disordered alloy This result is made unambiguous by c omparison to the ordered alloy whose hysteresis cycle of the phase transiti ons is dramatically different from the disordered alloy The pressure-depend ent collapse of the Curie temperature is the dominant mechanism for reducin g the magnetization only in the ordered alloy.