Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First Order Transition at the Curie Point of Gd5(SiXGe1-x)4

摘要

Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd(sub 5)(Si(sub x)Ge(sub 1-x))(sub 4) for x 0 (approx.) 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd(sub 5)(Si(sub 1.95)Ge(sub 2.05)), Gd(sub 5)(Si(sub 2)Ge(sub 2)), Gd(sub 5)(Si(sub 2.09)Ge(sub 1.91)), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd(sub 5)(Si(sub 0.15)Ge(sub 3.85)), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state.