Strain effects in epitaxial FeV2O4 thin films fabricated by pulsed laser deposition

• Epitaxial FeV2O4 spinel thin films were deposited by pulsed laser deposition.
• Fully relaxed films are tetragonal with c>a at room temperature.
• Different films on different substrates show different strain release mechanism.
• All the films have an out-of-plane magnetic easy axis independent of strain states.

The epitaxial c-axis orientated FeV2O4 films with different thicknesses on SrTiO3, LaAlO3 and MgAl2O4 (001) substrates were fabricated for the first time by pulsed laser deposition, and strain effects on the structure and magnetic anisotropy were investigated. The X-ray diffraction analysis shows that the lattice constants of the FeV2O4 films behave differently on different substrates. The compressive strain in the films on MgAl2O4 is dominantly controlled by the in-plane lattice mismatch. By contrast, the strain states in the films on LaAlO3 and SrTiO3 substrates can be explained by the difference in the thermal expansion coefficients between the films and substrates. In the temperature range investigated from 20 K to 300 K the fully relaxed FeV2O4 thick film is tetragonal with c>a, whereas its bulk is cubic. The magnetic easy axis of all the films is normal to the film plane, independent of substrates, film thickness, and strain states. The out-of-plane magnetic anisotropy is attributed to the high tetragonality with c>a due to the strong spin-lattice coupling.