FMR in multilayer magnetic thin films

We have used Ferromagnetic Resonance (FMR) to investigate a variety of coupled magnetic thin films. Two types of phenomena have been studied: (1) the interaction between a ferromagnetic and an antiferromagnetic layer (known as interfacial exchange anisotropy), (2) the interaction between two ferromagnetic layers separated by a non-magnetic interlayer.; In the first category we carried out experiments, with both 9 GHz and 33 GHz FMR spectrometers, on two systems: FeMn/NiFe and {dollar}alpha{dollar}-Fe{dollar}sb2{dollar}O{dollar}sb3{dollar}/NiFe. The exchange anisotropy field H{dollar}sb{lcub}rm E{rcub}{dollar} and the uniaxial anisotropy field H{dollar}sb{lcub}rm A{rcub}{dollar} were measured. The magnetic state of the interface was probed by FMR. Annealing experiments were done on these systems. After specific annealing procedures, the NiFe FMR spectrum in the FeMn/NiFe system was characterized by a sequence of spin wave resonance (SWR) modes. We documented the behaviour of these spin wave modes as a function of annealing conditions and specimen parameters. The evidence indicates that these spin wave modes are generated by "dynamic pinning" at the ferromagnetic/antiferromagnetic interface. We found that a dc magnetic field,. imposed during the annealing, affects the spin wave resonance spectrum. An attempt was made to correlate the magnetic properties (H{dollar}sb{lcub}rm E{rcub}{dollar}, spin wave behaviour, etc...) and the structural properties (grain size, texture, etc...).; In the second category we have examined both theoretically and experimentally the interaction of ferromagnetic layers through an intervening non-magnetic layer. We have worked out a model which predicts the number, positions, intensities and linewidths of the ferromagnetic resonance modes in such a system as a function of the coupling strength. Analyses were done both for ferromagnetic coupling and for antiferromagnetic coupling. Various orientations of the dc magnetic field with respect to the film normal were considered. We have done experiments on the Fe/Cu/Fe, NiFe/Ag/Ni and NiFe/SiO{dollar}sb2{dollar}/Ni film systems. Good agreement between experiment and theory for the FMR mode positions, intensities and linewidths was found. In Fe/Cu/Fe films the coupling strength K{dollar}spprime{dollar} was found to be small down to a CU thickness of 5 nm, but then to rise sharply at 2 nm. In the NiFe/Ag/Ni sequence, K{dollar}spprime{dollar} was found to vary as exp(-t{dollar}sb{lcub}rm Ag{rcub}/ tau{dollar}), with {dollar}tau{dollar} about 2.68 nm. An angular dependence of K{dollar}spprime{dollar} was suggested by comparison of data taken in this series at parallel and perpendicular applied dc field orientations. In the NiFe/SiO{dollar}sb2{dollar}Ni series, K{dollar}spprime{dollar} was found to be very small when compared to the one in the NiFe/Ag/Ni system. The results are consistent with the hypothesis that the major contribution to the coupling is through the polarization of the conduction electrons of the intermediate layer (RKKY interaction).