Magnet properties of Mn70Ga30 prepared by cold rolling and magnetic field annealing

The remanence and coercivity of arc melted Mn75Ga30 can be substantially improved by cold rolling. For best performance the rolled material should be annealed at T=730 K in the presence of a magnetic field of 1 T. The so-obtained magnet has a remanence of 0.239 T and a coercivity of 1.24 T at room temperature. The underlying reason for the high coercivity and remanence is the increase of the content of a metastable ferrimagnetic DO22 phase at the expense of the normally stable anti-ferromagnetic DO19. Magnetic field significantly increases the nucleation rate of the ferromagnetic DO22 phase that leads to grain size refinement and as a consequence of improving remanence and coercive field.