POLARIZED NEUTRON REFLECTION STUDY OF THE UNIDIRECTIONAL MAGNETIC-ANISOTROPY OF PERMALLOY ON NI0.5CO0.5O

Couples of ferromagnetic Permalloy/antiferromagnetic metal oxide exhibit unidirectional magnetic anisotropy along a magnetic field applied during cooling. Polarized neutron reflection has been used to check if the effect is due to a bias of the antiferromagnetic configuration in the oxide, where the layer immediately adjacent to the Permalloy is polarized parallel to the easy direction of magnetization. The measurements were made on a sample consisting of 300 angstrom Permalloy/500 angstrom Ni0.5Co0.5O. Polarized neutron reflectivities were taken at the four corners of the magnetic hysteresis loop at 20 K. A faint magnetic signal consistent with the unidirectional bias of the F/AF structure was observed. This behavior is discussed in the light of the current theories.