Effect of a magnetic field on the magnetostructural phase transition in Gd5(SixGe1-x)4

The first-order magnetostructural phase transition in Gd-5(SixGe1-x)(4) alloys with xless than or equal to0.5 and the related entropy change DeltaS 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 xless than or equal to0.5 range. From these data, the ratio dH(t)/dT(t), which is related to the strength of the magnetoelastic coupling, is obtained as a function of x. We show that DeltaS obtained from the Clausius-Clapyeron equation and the Maxwell relation are equivalent for all compositions (0less than or equal toxless than or equal to0.5), provided the Maxwell relation is evaluated only within the transition region. The T and H dependences of DeltaS are accounted for by modeling the T and H dependences of the magnetization outside the transition