Thickness dependence of magnetic properties in submicron yttrium iron garnet films

Yttrium iron garnet (YIG) films with various thicknesses have been fabricated by liquid-phase epitaxy (LPE) on gadolinium gallium garnet (GGG) (1 1 1) substrates showing unusual magnetic properties. In this work, we studied YIG films with thicknesses between 100 nm and 1000 nm and compared them with La3+-doped YIG films (La:YIG) over a similar scale. The relaxation of tensile stress at the GGG/YIG interface, which caused a magnetic hysteresis loop, showed an easy magnetization phase for thin YIG films (≤400 nm), while a hard magnetization phase gradually appeared with further increases to the film thickness. The stable magnetic properties of La:YIG at different thicknesses and the not so perfect magnetic hysteresis loop are caused by the intrinsic distortion of the sublattice from La3+ partially replacing Y3+. The saturation magnetization field (4πM s) obtained from broadband ferromagnetic resonance measurement of the YIG films increased with increasing H a and stayed around the theoretical value. This work helps us to understand the properties of LPE-based YIG films and devices at the sub-microscale.