Magnetic resonance study and computer simulation for the induced unidirectional anisotropy of reentrant Ni-Mn alloys

Microwave resonance studies are reported on the ${\mathrm{Ni}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$ (x=0.230 and x=0.255) alloys in the temperature range 4.2–300 K. By fitting the resonance lines to the solutions of the Landau-Lifshitz equation for the metallic ferromagnetic systems and considering both parallel and perpendicular magnetization for the thin disklike specimen, we have obtained the macroscopic anisotropy $H_A^{\mathcal{’}}$ and linewidths ΔH, as a function of temperature for both the zero-field cooling and field cooling cases. We conclude that the main contribution to the anisotropy comes from Dzyaloshinsky-Moriya–type interaction between the frustrated spins within the domains, while the contribution of the spins in the domain walls is negligible. We also confirm that the induced anisotropy can be rotated elastically by the internal effective field.