Investigation of the Domain Structure of Sm2Fe17Nx Intermetallic Nitrides

In the present work the change of the easy magnetization direction from easy plane to easy axis of the primary compound Sm2Fe17 by absorbing nitrogen is directly observed by the domain pattern. The intrinsic magnetic parameters of nitrided Sm2Fe17Nx such as domain wall energy γ, average exchange constant A, domain wall width δB, as well as the critical diameter of single domain particles Dc are estimated. The domain behavior of Sm2Fe17Nx under the applied external field is also investigated. Our results indicate that the nuclei initially occurring in the bulk of the grain are weakly pinned and that the coercivity of the material is dominated by the nucleation occurring at the surface of the grain, which is relative larger than the pinning field within the grain. In the Sm2Fe17N2.15 compound, a three-dimensional domain pattern is observed, which directly gives an experimental support of Goodenough's assumption that the walls are slabs in the main body and zigzag undulatory walls with a decreasing amplitude of undulations with increasing distance from the surface.