Polarized neutron reflection study of the unidirectional magnetic anisotropy of permalloy on Ni(sub 0.5)Co(sub 0.5)O

摘要

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 permalloy/500(Angstrom) Ni(sub 0.05)Co(sub 0.5)O. The polarized neutron reflectivities taken at the four corners of the magnetic hysteresis loop at 20K. A faint magnetic signal consistent with the unidirectional bias of the F/AF structure is also observed. This behavior is discussed in the light of the current theories.