Magnetic-Field-Induced Enhancement of Phase Transformation in Ferromagnetic tau-Mn-Al

The magnetic field effect on phase formations of ferromagnetic Mn-Al(tau-phase) was evaluated. The transformation from epsilon-phase with hcp-structure to tau-phase was accelerated by annealing in magnetic field. With in-field annealing at 623 K, the magnetization of the sample annealed at 15 T was a maximum of 72.2 A.m(2)/kg at 1.5 T, which was over 4 times larger than that annealed in a zero field. Meanwhile, the precipitation of non-ferromagnetic beta-phase was suppressed by in-field annealing. Magnetic field-induced acceleration of epsilon-tau transformation and suppression of tau-beta transformation were due to the gain of Zeeman energy of tau-phase.