Experiments on the extraordinary Hall effect in sputtered amorphous rare-earth–cobalt films show that the effect is due to the cobalt magnetization rather than that of the rare earth.

No abstract

The magnetic properties—as determined by ferromagnetic resonance (FMR) measurements—lattice strain Δa/a and variation of these parameters were studied as a function of annealing temperatue Tann in (YSmLuCa)3(FeGe)5O12 bubble garnet films subjected to a triple implantation by H+ ions. On the as-implanted sample the FMR spectrum and Δa/a could not be measured. On samples annealed at 200 °C three resonance peaks appear corresponding to three sublayers with different magnetic properties. The formation of the sublayers is related to the inhomogeneous distribution of H+ ions along the implanted layer as a result of the triple implantation. For this range of Tann the Curie temperature TC, Δa/a, and the anisotropy fields vary strongly with annealing time. This result is related to the high diffusion rate of hydrogen and shows that the magnetic properties are substantially modified by the absorbed H+ ions. When Tann>300 °C the amount of H+ incorporated becomes negligible, so the magnetic parameters and the value of Δa/a are essentially determined by the lattice damage. The implanted layer becomes magnetically homogeneous as shown by a well-defined spin wave spectrum characteristic of a layer with fairly uniform magnetic properties along its thickness. For 300 °C<Tann<600 °C increasing Tann results in a decrease of Δa/a and a restoration of the superexchange interaction between the a and d sites, as shown by the increase of TC. The resonance linewidth ΔH1 of the implanted layer is greatly reduced with respect to ΔH0 of the bulk of the film, due to the fact that a large part of c site rare-earth ions are decoupled from the garnet system. As a consequence, Ku is negligible and λ111 is strongly reduced in the implanted layer. For Tann>630 °C the rare-earch ions are progressively recoupled as shown by the increase of ΔH1. As a result λ111 increases and Ku is partially restored.

The domain structures of garnets and amorphous films have been studied with magnetic colloid in reflected polarised light. An enhancement of contrast at the domain walls is noted, the nature and origin of which are discussed. Some practical applications of the technique are mentioned.

Transport methods using high speed photography and ferromagnetic resonance are compared for the determination of the dynamic characteristics of bubble materials. The mobility and the saturation velocity are calculated with the use of parallel and perpendicular magnetic resonance fields and linewidth. Experiments are performed with 2-μm bubbles Ga, Al or (Ca, Ge) substituted (Eu, Lu)3 Fe5 O12 and (Y Sm Lu Ca)3 (Fe Ge)5 O12 garnet films. In films experimented with, the mobilities range between 400 and 1000 cm/S Oe and the saturation velocities between 800 and 2000 cm/s. A good agreement has been found between both methods.