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

Abstract

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 $T_{c} \approx 300$ 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 Ni2MnGa phase after the annealing can be responsible for the magnetic hardening and the change of the Curie temperature.