Interfacial spin structures in Pt/Tb₃Fe₅O₁₂ bilayer films on Gd₃Ga₅O₁₂ substrates

Abstract

In this study, we investigate the properties of ferrimagnetic Tb3Fe5O12 (TbIG) thin films grown on Gd3Ga5O12 (GGG) substrates using the pulsed laser deposition technique. Some of the films are capped with a thin platinum (Pt) layer. We observe a strong temperature-dependent anomalous Hall effect in the films, with sign reversals at the ferrimagnetic compensation temperature (∼240K) and lower temperatures. X-ray diffraction and scanning transmission electron microscopy (STEM) confirm the high crystalline quality and smooth surfaces of the films, while the Pt layer is found to be polycrystalline. Polarized neutron reflectometry reveals a weak magnetic moment confined to the TbIG layer, and an interfacial magnetic layer at the substrate-film boundary appears at low temperatures (below 10 K). This observation is supported by STEM-energy dispersive x-ray mapping, which indicates a chemical difference in the ratio of Gd:Ga at the TbIG/GGG interface. Unlike YIG/GGG interfaces, the TbIG/GGG interface does not exhibit magnetic dead layers. Additionally, a small, induced magnetization is detected in the Pt heavy metal layer at low temperature, with ferromagnetic coupling to the garnet, potentially influencing the anomalous Hall effect.