摻雜釤和鐿元素的釔鐵石榴石的垂直磁異向性的探討

Yttrium iron garnet (YIG) is a magnetic insulator, whose magnetic easy axis oriented along [111] crystalline direction. YIG was intensively studied in 1980s-1990s due to its large magneto-optical Faraday effect and small spin wave damping in wide spectral range. For its small spin wave damping properties, YIG is recently applied to study spin pumping and spin transfer in (Au,Pt,Ta)/YIG and topological insulator/YIG heterostructures, with the intention of future spintronic application of information transfer by means of spin wave packets instead of current carriers. For the applications in nanoscale, it is important to orient the magnetic easy axis perpendicular to the thin film surface. However, due to strong shape anisotropy, YIG thin films grown on lattice matched (111)-oriented gadolinium gallium garnet substrate have the magnetic easy axis in the surface plane. Recently, clear strain-induced perpendicular magnetic anisotropy in YIG(111) thin films grown on lattice mismatched substrates was reported. Therefore, we are going study the effect of strain on perpendicular magnetic anisotropy of YIG thin films by changing its lattice constant with doping of thulium(Tm) as well as growth on lattice mismatched substrates such as c-oriented sapphire. The thin films will be grown by pulsed-laser deposition, and the composition, structural, optical, transport, and magnetic properties of TmYIG. We are going to demonstrate the perpendicular magnetic anisotropy and to determine the magnitude of the strain effect. Furthermore, we are going to study the spin pumping and spin transport with the heterostructures based on SmYIG and YbYIG with perpendicular magnetic anisotropy. Chemical composition analysis revealed difference between Tm density in thin films and the nominal Density, indicating existence of secondary phases. Structural investigations showed that the thin films are poly-crystalline, and that the secondary phases consist of Tm2O3, YFeO3, and Fe2O3. Surface morphology study showed the poly-crystalline thin film having Rough Surface, about 20 nm of roughness. Magnetic investigations showed all thin films without magnetic order and anisotropy.