Tunable magnetocaloric effect in Gd-based glassy ribbons

Abstract

The series of glassy ribbons Gd60M30In10 (M = Mn, Co, Ni, Cu) was synthesized by melt-spinning. The change of transition element M in these Gd-based metallic glasses was proven to induce huge variations of the Curie temperature TC, magnetic entropy change peak values ΔSmpeak, and widths at half maximum values of the magnetic entropy change δT. When M is non magnetic (M = Co, Ni, Cu), the samples behave similarly: they display high values of ΔSmpeak (between -6.6 and -8.2 J/kg K in a magnetic field variation of 4.6 T), average δT values (between 77 and 120 K) and no magnetic hysteresis. On the contrary, when M carries a magnetic moment (M = Mn), some irreversibility appears at low temperature, ΔSmpeak is lower (only 3.1 J/kg K for μ0H = 4.6 T) and the magnetic transition is very large (δT = 199 K for μ0H = 4.6 T). These features are explained by some antiparallel coupling between Mn atoms randomly located in the metallic glass. This leads to the occurrence of a cluster-glass behavior at low temperature (35 K), following the ferromagnetic transition observed at 180 K when the temperature is decreased. Also, power law fittings of ΔSmpeak and δT versus μ0H were performed and show that δT is less field dependent than ΔSmpeak. We could then identify an interesting way of improving the refrigeration capacity of the material at low magnetic field.