Thickness dependence of magnetic properties in submicron yttrium iron garnet films

Yttrium iron garnet (YIG) films with various thicknesses have been fabricated by liquidphase 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 (4pMs) obtained from broadband ferromagnetic resonance measurement of the YIG films increased with increasing Ha 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.