Triad Anisotropy and Magnetization Reversal by 180° Domain Wall in ReentrantNi79Mn21

Magnetic and magnetotransport measurements on ${\mathrm{Ni}}_{79}$ ${\mathrm{Mn}}_{21}$ reentrant alloy are reported. When the specimen is cooled in a field $H$, both the magnetoresistance and its field derivative exhibit a sharp jump at the same field as magnetization. Evidence is given that (1) magnetization reversal is dominated by 180°-domain-wall propagation and (2) this is a direct consequence of the triad symmetry of Dzyaloshinsky-Moriya anisotropy which generally stabilizes the 180° domain wall and destabilizes other wall configurations.