Stress-Induced Perpendicular Magnetization in Epitaxial Iron Garnet Thin Films

We have grown pseudomorphic Tm 3 Fe 5 O 12 films (46–350 nm in thickness) with perpendicular magnetization on (111) Gd 3 Ga 5 O 12 substrates. Among various garnets, Tm 3 Fe 5 O 12 is selected because of a negatively large magnetostriction constant to overcome strong shape anisotropy in very thin films. A stress-induced anisotropy field as large as +25 kOe is estimated by calculation under a moderate in-plane tensile strain of +0.49%. The magnetization hysteresis loop and magnetic domain structure indicate the perpendicular easy axis. The domain size ( W ) in its maze pattern varies from 500 to 960 nm with increasing thickness ( t ) and agrees well with a scaling law of W ∝√t.