Magnetization profile and magnetocrystalline anisotropy of ferromagnet-semiconductor heterostructure systems

Ab initio linear-muffin-tin orbital calculations of the magnetization profile and the magnetic anisotropy of ferromagnetic-semiconductor (FM/SC) multilayers, bcc Fe/Ge (001) and bcc Fe/GaAs (001), have been carried out to find out the microscopic origin of these properties. The electronic magnetic anisotropy energy (MAE), computed with the force method, was found to favor a magnetization perpendicular to the plane of the layers and to increase with the thickness of the ferromagnetic layers. The anisotropy of the energy, i.e., the MAE, as well as the anisotropy of the orbital magnetic moment turned out to depend only slightly on the type of semiconductor, Ge or GaAs, and to come mainly from the interface Fe layers. In particular, it was found that the relationship between the electronic MAE and the anisotropy of the orbital moment proposed by van der Laan is very well satisfied in these systems. According to that relationship, the magnetic anisotropy of these FM/SC multilayers is mainly due $(\sim 80–90\%)$ to a delicate rearrangement of the occupations of certain $3d$ spin down levels in the interface Fe layers caused by the change of the magnetization direction.