Magnetization reversal processes in hot-extruded τ-MnAl-C

Abstract The magnetic domain structure of hot-extruded bulk τ-Mn 53 Al 45 C 2 was studied by Kerr microscopy under application of a magnetic field in-situ. The microstructure consists of recrystallized, fine-grained regions and large non-recrystallized grains which contain a high density of twins. Within these large polytwinned grains, a clear pinning interaction of magnetic domain walls at twin boundaries was observed but with a rather small pinning force. The smaller, recrystallized grains show a higher resistance to magnetization reversal. The critical single domain particle size of this material was estimated at 773 nm and the fine, recrystallized grains are in the range of this size. Demagnetizing the sample following saturation using a 3 T field pulse revealed that individual fine grains reverse independently from their neighbours.

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