single crystal studied by angle-dependent x-ray magnetic circular dichroism

(Ba_,K)(Zn,Mn)₂As₂ is a new ferromagnetic semiconductor isostructural to 122-type Fe-based superconductors. The Curie temperature (T_C) reaches 230 K for polycrystalline samples exceeding the highest T_C = 200 K of (Ga,Mn)As. In relation to the anisotropic crystal structure, this material has large perpendicular magnetic anisotropy.
In the present study, we have investigated the origin of the perpendicular magnetic anisotropy by angle-dependent x-ray magnetic circular dichroism (AD-XMCD) measurements. The XMCD spectra were similar to those of (Ga,Mn)As and showed multiplet features. This indicates the localized nature of the Mn 3d electrons being consistent with the carrier-induced-ferromagnetism scenario. The angle-dependent measurements yielded the anisotropy field of 0.8 T. The XMCD spectra taken under the transverse geometry (TXMCD), where the spin aligns perpendicular to the x ray, showed finite dichroic signals. This originates from the aspherical distribution of 3d electrons, and indeed the TXMCD spectra were reproduced by the configuration interaction cluster-model calculation incorporating D_4h crystal-field splitting. We suggest that degenerate p-d_xz,yz hybridized orbitals at the Fermi level are responsible for the magnetic anisotropy of this compound.