Tuning the magnetocaloric response of Er-based metallic glasses by varying structural order in disorder

The effects of structural order on magnetocaloric response have been explored in Er60Al16Co20Ni4 metallic glass (MG). Compared with the fully amorphous structure of the as-spun ribbon (cooling rate ∼106 K/s), the rod sample fabricated with a lower cooling rate (∼103 K/s) contains a few crystalline phases embedded in the amorphous matrix. Annealing the ribbon in the supercooled liquid region results in formation of a large amount of nanocrystalline phase. Both the as-spun ribbon and rod samples show a single spin-glass-like transition behavior, while the annealed sample exhibits double-freezing processes. It is found that the sparsely distributed micro-sized crystalline phases (content fraction of 13%) exert a slight effect on the magnetic entropy change (MEC). However, densely distributed nanocrystallization phase (∼50%) in amorphous matrix leads to an obvious reduction of the MEC and refrigerant capacity (RC). The exponent n of field dependence of MEC is found to related to exchange frustration, random anisotropy, and structure ordering degrees.