The magnetic anisotropy (MA) of Fe-based ferromagnetic thin films has been extensively studied for device applications. The examined material is a new Fe-based ferromagnetic thin film, bcc $\mathrm{F}{\mathrm{e}}_{1-x}\mathrm{A}{\mathrm{s}}_x$ (Fe–As) with in-plane MA (IMA) grown on a GaAs (111)B substrate. The magnetic properties of the Fe–As thin film have been investigated by X-ray magnetic circular dichroism (XMCD) and magnetic circular dichroism in hard X-ray photoemission spectroscopy (MCD-HAXPES) to elucidate the role of As ions in the IMA. The XMCD spectra at the Fe $L_{2,3}$ edge and MCD-HAXPES spectra of the Fe $2p$ core level exhibit ferromagnetic and metallic features similar to those of Fe metal. The XMCD at the As $L_{2,3}$ edge demonstrates that the As ions contribute to the anisotropic ferromagnetism of bcc Fe–As through hybridization between the Fe $3d$ and As $4p$ orbitals. Estimates of the magnetic moments of Fe using the XMCD sum rules reveal that the orbital magnetic moment is isotropic and the magnetic dipole term is anisotropic. In comparison with the undoped Fe film, the anisotropy of the magnetic dipole term can be attributed to the anisotropic $p–d$ hybridization induced by epitaxial strain, contributing to the enhancement of the IMA in bcc Fe–As.

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• Magnetism
• Spintronics
• Hard x-ray photoelectron spectroscopy
• X-ray magnetic circular dichroism