Evidence for Antiferromagnetic Coupling in Ag/Ni Superlattices: a Neutron Scattering Study

Low-angle neutron scattering experiments in reflection geometry have been performed on Ag/Ni superlattices prepared by sputtering. The low-temperature diffraction diagram shows the appearance of a supplementary low-angle peak attributed to the doubling of the chemical period, as a consequence of the antiparallel alignment of the magnetic moments in successive nickel layers. The variation of the intensity of this antiferromagnetic peak with applied magnetic field is in accordance with a classical model of antiferromagnetism in which the magnetic moments, at first perpendicular to the field, rotate progressively to the direction of the field. A good agreement is found with magnetization and magnetoresistance results obtained on the same samples.