SPIN-POLARIZED SECONDARY-ELECTRON MICROSCOPY OF SOFT-MAGNETIC FILMS ON ANTIFERROMAGNETIC SUBSTRATES

Coupling of soft magnetic films to antiferromagnetic substrates was st udied by spin-polarized secondary electron microscopy. Permalloy (Ni80 Fe20 alloy) films were deposited on antiferromagnetic NiO(111) single- crystal substrates. A domain structure consisting of fine grains (simi lar to 50 mu m) 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 de magnetic field, man y of the fine grains disappeared and the film showed large domains (si milar to 1 mm). In the large domains, small elongated reversed domains (similar to 20 mu m x 60 mu m) aligned parallel to each other implyin g local easy axis of magnetization. The type of domain behavior descri bed above was not observed in a NiFe film on MgO(111) substrate that h ad the same crystal structure as NiO but no magnetic ordering. An x-ra y analysis revealed that the local easy axes observed in NiFe/NiO spec imens coincided with the [11 (2) over bar] of the NiO crystal lying in the (111) substrate plane, which supported coupling of the NiFe film with the single-crystal substrate. (C) 1997 American Institute of Phys ics.