Controllable ferromagnetic/re-entrant spin glass state and magnetocaloric response of Gd-Er-Al-Co metallic glasses

The effects of random anisotropy on the magnetic transition and magnetic entropy change (MEC) have been investigated in a series of Gd-Er-Al-Co metallic glasses(MGs) through Er addition. The Gd-based metallic glass without Er shows typical ferromagnetic transition. With Er addition, the Curie temperature decreases and a re-entrant spin glass like behavior can be observed due to the frustration among random magnetic anisotropy (RMA) and exchange interactions. A large maximum MEC of 9.1 J kg−1 K−1 around 117.5 K is obtained in Gd56Co24Al20 MG, which can be tuned continuously in a wide temperature range (117.5-17.5 K) by introducing Er without impairing the good glass forming ability. A largest peak MEC of 12.6 J kg−1 K−1 has been obtained around 17.5 K in Gd8Er48Co24Al20. Significantly, the exponent n of field dependence of MEC is found to depend on the degree of magnetic frustration among RMA and exchange interactions.