Optimized growth of compensated ferrimagnetic insulator Gd₃Fe₅O₁₂ with a perpendicular magnetic anisotropy*

Abstract

Compensated ferrimagnetic insulators are particularly interesting for enabling functional spintronic, optical, and microwave devices. Among many different garnets, Gd3Fe5O12 (GdIG) is a representative compensated ferrimagnetic insulator. In this paper, we will study the evolution of the surface morphology, the magnetic properties, and the magnetization compensation through changing the following parameters: the annealing temperature, the growth temperature, the annealing duration, and the choice of different single crystalline garnet substrates. Our objective is to find the optimized growth condition of the GdIG films, for the purpose of achieving a strong perpendicular magnetic anisotropy (PMA) and a flat surface, together with a small effective damping parameter. Through our experiments, we have found that the surface roughness approaching 0.15 nm can be obtained by choosing the growth temperature around 700 °C, together with an enhanced PMA. We have also found the modulation of magnetic anisotropy by choosing different single crystalline garnet substrates which change the tensile strain to the compressive strain. A measure of the effective magnetic damping parameter (α eff = 0.04±0.01) through a spin pumping experiment in a GdIG/Pt bilayer is also made. Through optimizing the growth dynamics of GdIG films, our results could be useful for synthesizing garnet films with a PMA, which could be beneficial for the future development of ferrimagnetic spintronics.

Scaling of the Thermally Induced Sign Inversion of Longitudinal Spin Seebeck Effect in a Compensated Ferrimagnet: Role of Magnetic Anisotropy

“…[54][55][56][57] The lattice constant of bulk GdIG is a GdIG,bulk = 1.2471 nm, whereas that for single crystalline GSGG substrate is a GdIG,film = 1.2554 nm. [58] Hence, the GdIG thin film grown epitaxially on a GSGG substrate exhibits an in-plane lattice constant >1.2471 nm, introducing tensile in-plane strain in the film, given by GdIG,bulk G dIG,film GdIG, bulk a a a…”

“…[ 54–57 ] The lattice constant of bulk GdIG is a GdIG,bulk = 1.2471 nm, whereas that for single crystalline GSGG substrate is a GdIG,film = 1.2554 nm. [ 58 ] Hence, the GdIG thin film grown epitaxially on a GSGG substrate exhibits an in‐plane lattice constant >1.2471 nm, introducing tensile in‐plane strain in the film, given by . Consequently, thin films grown on GGG strengthen the in‐plane alignment of the magnetic easy axis, while for films grown on GSGG, magnetoelastic and magnetic shape anisotropy counteract each other, and PMA can be achieved at room temperature.…”

The 50 nm-thick yttrium iron garnet films with perpendicular magnetic anisotropy

“…[7] So far, many research groups have obtained PMA in different magnetic garnet thin films by growing them on lattice mismatched non-magnetic garnet substrates. [8][9][10][11][12][13][14][15][16][17][18] Particularly, there are several works indicating that yttrium iron garnet (YIG) thin films, which have lower inherent α than any other magnetic material, [19] could obtain perpendicular magnetization if an appropriate non-magnetic garnet substrate was chosen. [20][21][22][23] For example, the PMA YIG films grown on GSGG by Ding et al [23] have α lower than 5 × 10 −4 .…”