Spin-polarized secondary electron microscopy of soft magnetic films on antiferromagnetic substrates

Coupling of soft magnetic films to antiferromagnetic substrates was studied by spin-polarized secondary electron microscopy. Permalloy (Ni80Fe20 alloy) films were deposited on antiferromagnetic NiO(111) single-crystal substrates. A domain structure consisting of fine grains (∼50 μm) was characteristic of the NiFe film deposited without applying magnetic field. The domain image and its response to applied field suggested existance of local easy axis and local unidirectional anisotropy. When macroscopic unidirectional anisotropy was introduced to the NiFe film by depositing under an applied dc magnetic field, many of the fine grains disappeared and the film showed large domains (∼1 mm). In the large domains, small elongated reversed domains (∼20 μm×60 μm) aligned parallel to each other implying local easy axis of magnetization. The type of domain behavior described above was not observed in a NiFe film on MgO(111) substrate that had the same crystal structure as NiO but no magnetic ordering. An x-ray analys...