Tunable magnetocaloric effect in Gd-based glassy ribbons

The series of glassy ribbons Gd 60 M 30 In 10 ( M ¼ 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 T C , magnetic entropy change peak values D S m peak , and widths at half maximum values of the magnetic entropy change d T. When M is non magnetic ( M ¼ Co, Ni, Cu), the samples behave similarly: they display high values of D S m peak (between -6.6 and -8.2 J/kg K in a magnetic field variation of 4.6 T), average d T values (between 77 and 120 K) and no magnetic hysteresis. On the contrary, when M carries a magnetic moment ( M ¼ Mn), some irrever- sibility appears at low temperature, D S m peak is lower (only 3.1 J/kg K for l 0 H ¼ 4.6 T) and the magnetic transition is very large ( d T ¼ 199 K for l 0 H ¼ 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 D S m peak and d T versus l 0 H were performed and show that d T is less field dependent than D S m peak .We could then identify an interesting way of improving the refrigeration capacity of the material at low magnetic field.