Magnetic and some crystalline properties of H+ ion-implanted garnet layers: A study as a function of annealing treatment

Publisher Website
Google Scholar
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<TannTann 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.