Magnetic Properties and Structure of Metallic Multilayers Investigated by NMR

ABSTRACTAs a probe of the short range chemical and topological order, NMR is useful for structural investigations of magnetic multilayers (interface structure and composition, bulk phases and defects, strains). The magnetic character of the raw data makes it also possible to study local magnetic properties of these composite systems, and to correlate them with local structural features. The hyperfine field is the first output of an NMR experiment which gives a direct insight on the local magnetization in ferromagnets. NMR is also sensitive to the restoring torque exerted on the electronic moment by the local magnetic anisotropy and/or exchange and dipolar couplings. Combined with the fact that the various parts of a sample (atomic planes involved in the interfaces, bulk phases and bulk defects) can be discriminated in the spectra, the magnetic information contained in the data allows to probe quantitatively or, at least, to place on a relative scale, the different magnetic responses of the different parts of a sample. We present here the relevant results which we have obtained in the course of our investigations of Co based multilayers and spin valves (interface magnetic profiles, inhomogeneities of magnetic anisotropy and of magnetic coupling).