Epitaxial growth and magnetodielectric properties of terbium-iron-garnet thin films

We report on the (110)-oriented epitaxial growth of terbium-iron-garnet (Tb₃Fe₅O₁₂, TbIG) thin films on Pt(111)/Gd ₃Ga₅O₁₂ (110) substrates by pulsed laser deposition, and their dielectric and magnetodielectric properties. High-quality TbIG thin films with clear interfaces can be achieved at a 750°C substrate temperature and a 120 mTorr oxygen partial pressure, with subsequent annealing at 900°C in air. The thickness of Pt is found to be crucial for epitaxial growth of TbIG and is optimized at 35 nm. The temperature-dependent dielectric constant shows a clear kink near 150 K due to a structural transition, similar to that of a single crystal. However, the magnetic field dependence of the dielectric constant is an order of magnitude smaller than that of a single crystal and appears only when applied magnetic and electric fields are normal to the film plane, a sharp contrast to the case of a single crystal. We have attributed such differences to the rotation of magnetic easy axis from [1-11] to [110] and to the reduced magnetostriction due to the clamping effect from the substrate.