Grain refinement leading to the ultra-high coercivity in L10-Mn1.33Ga bulk magnet via hot deformation

We achieved ultra-high coercivity of 5.65 kOe in L1(0)-Mn1.33Ga alloy via the hot deformation (HD) method and revealed the hardening mechanism. Hot deformation led to recrystallization and grain refinement, where the average grain size was reduced to about 1.5 mu m for HD-88% magnet. The coercivity mechanism indicated a weak pinning model by magnetic mini-loop analysis. It was found that small grains were formed, accompanied by a certain number of {111} < 11-2 > twins for HD magnets. The magnetic domain observation showed that both the sub-micro grain boundary and the twin boundary were acted as the pinning center of the domain wall, but the latter had weaker pinning effect. The ultra-high coercivity of the HD-88% Mn1.33Ga magnet originated mainly from the pinning of the grain boundary enhanced by grain refinement. Further grain refinement and twin structure inhibition will be promising approaches in order to obtain higher magnetic properties for L1(0)-MnxGa bulk magnets. Published under an exclusive license by AIP Publishing.

Automated summary

We achieved ultra-high coercivity in the L1(0)-Mn1.33Ga alloy through hot deformation and identified the hardening mechanism. The hot deformation process resulted in recrystallization and grain refinement, leading to enhanced grain boundary pinning. The magnetic domain observation revealed that both the sub-micro grain boundary and the twin boundary acted as pinning centers for the domain wall.