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

7 pags., 6 figs.The evolution of the magnetic anisotropy directions has been studied in a magnetite (FeO) thin film grown by infrared pulsed-laser deposition on SrTiO(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° 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, 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 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 and 〈110〉 for T < T. These results provide a clear proof of the possibility of tuning magnetic anisotropy in FeO thin films by proper control on the growth parameters and substrate choice.This research was supported by the Regional Government of Madrid through NANOMAGCOST project (P2018/NMT-4321) and by the Spanish Ministry of Economy and Competitiveness (MINECO) through Project CTQ2016-75880-P. M. O. thanks CSIC for contract and E. R. thanks MINECO for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069). The work in Lausanne was supported by the Sinergia grant “Mott physics beyond the Heisenberg model” of the Swiss NSF. The work in BUTE (Hungary) was supported by NKFIH Grant No. K119442 and 2017-1.2.1-NKP-2017-00001, and by the BME-Nanotechnology FIKP grant of EMMI (BME FIKP-NAT). IMDEA Nanoscience is supported by the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D, MINECO [grant number SEV-2016-0686