Effect of a magnetic field on the magnetostructural phase transition in Gd_5(Si_xGe_(1-x))_4

摘要

The first-order magnetostructural phase transition in Gd_5(Si_xGe_(1-x))_4 alloys with x≤0.5 and the related entropy change ΔS are analyzed from high-field magnetization curves up to 23 T, and differential scanning calorimetry up to 5 T. The variation of the transition field H_t with the transition temperature T_t is discussed for fields up to 23 T for the x≤0.5 range. From these data, the ratio dH_t/dT_t, which is related to the strength of the magnetpelastic coupling, is obtained as a function of x. We show that ΔS obtained from the Clausius-Clapyeron equation and the Maxwell relation are equivalent for all compositions (0≤x≤0.5), provided the Maxwell relation is evaluated only within the transition region. The T and H dependences of ΔS are accounted for by modeling the T and H dependences of the magnetization outside the transition.