Nanoscale Ga/Al substituted yttrium iron garnet films by liquid phase epitaxy

Yttrium iron garnet (YIG) has minimum damping factor and low ferromagnetic resonance (FMR) linewidth, making it a preferred material for low loss microwave and spintronic devices. The saturation magnetization of YIG is 1750 Gauss, and for low-frequency devices, a lower saturation magnetization is more suitable. Ga3+ and Al3+ are with smaller radii and non-magnetic moment, so the substitution of Ga3+ and Al3+ can decrease saturation magnetization. Here, 4.8–193.7 nm ultra-thin Y3(GaAlFe)5O12 garnet (GaAl-YIG) monocrystalline films are prepared on gadolinium gallium garnet (GGG) substrates by using the liquid-phase epitaxy (LPE) method. As expected, these films exhibit a low saturation magnetization of almost less than 100 Gauss, while their FMR linewidth remains at levels close to that of YIG. The films show a (111) orientation and in a state of tension, and the diffraction intensity of the films get stronger as films thickness increases. The free energy and density of states are calculated for different Ga/Al substitution position by density functional theory simulations. The elements show a different diffusion distance in the GaAl-YIG/GGG interface, and the variation of magnetization properties with interface width are analyzed. The surface roughness of the films is only a few angstroms. The damping factor of these ultra-thin films are on an order of 10−4 except the 4.8 nm film, which suggests that the minimum thickness of the garnet film with good performance by using the LPE method is about 10 nm. According to the analysis of structure and magnetization properties, it demonstrates that the LPE method has potential to provide nanoscale garnet films for low loss microwave and spintronic devices.