Tuning of Magnetic Properties of Ni–Mn–Ga Glass-Coated Microwires

We have observed that annealing conditions strongly affect the temperature dependence of magnetization and Curie temperature of NiMnGa glass-coated microwires. After long (6 h) annealing of the microwires at 773 K, a ferromagnetic ordering is obtained with T
_c
≈ 300 K, which is beneficial for a magnetic solid-state refrigeration. The annealed samples also exhibit the exchange bias effect at low temperatures. The decomposition of GaNi phase and the precipitation of Ni
₂
MnGa phase after the annealing can be responsible for the magnetic hardening and the change of the Curie temperature.