Specific heat of EuxSr1-xS in high magnetic fields.

Abstract

The specific heat C of the spin glass ${\mathrm{Eu}}_{0.25}$${\mathrm{Sr}}_{0.75}$S and of the reentrant ferromagnet ${\mathrm{Eu}}_{0.54}$${\mathrm{Sr}}_{0.46}$S has been measured between 70 mK and 2 K in magnetic fields B up to 6 T. C for B=0 varies roughly linearly with temperature as found previously, while the steep temperature dependence observed in high fields indicates the gradual opening of a gap in the energy spectrum with increasing B. The presence of a large threshold field ${B}_{0}$ for the existence of a gap in the case of the spin glass is attributed to a peak in the density of states in the vicinity of E=0, in agreement with recent numerical calculations.