Evidence of anomalous switching of the in-plane magnetic easy axis with temperature in Fe3O4 film on SrTiO3:Nb by v-MOKE and ferromagnetic resonance

摘要

The evolution of the magnetic anisotropy directions has been studied in a magnetite (Fe3O4) thin film grown by infrared pulsed-laser deposition on SrTiO3(100):Nb substrate. The magnetic easy axes at room temperature are found along the in-plane 100 film directions, which means a rotation of the easy axis by 45 degrees with respect to the directions typically reported for bulk magnetite and films grown on single-crystal substrates. Moreover, when undergoing the Verwey transition temperature, T-V, the easy axis orientation evolves to the 110 film directions. This anomalous behavior has been demonstrated by measuring first the angular dependence of coercivity and remanence well above and below T-V by high-resolution vectorial magneto-optical Kerr effect (v-MOKE). Ferromagnetic resonance (FMR) measurements have additionally proven a well-defined fourfold magnetic anisotropy induced during growth with confirmed easy axis directions along 100 for T > T-V and 110 for T < T-V. These results provide a clear proof of the possibility of tuning magnetic anisotropy in Fe3O4 thin films by proper control on the growth parameters and substrate choice.