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

• Published in: Nanoscale 2019-10, Vol.11 (42), p.1987-19876
• Main Authors: Cuñado, José Luis Fdez, Camarero, Julio, Pedrosa, Francisco J, Nemes, Norbert M, Sanz, Mikel, Oujja, Mohamed, Rebollar, Esther, Marco, José F, de la Figuera, Juan, Monti, Matteo, Castillejo, Marta, Feher, Titusz, Nafradi, Balint, Forró, Laszlo, Bollero, Alberto
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c9nr04198b

The evolution of the magnetic anisotropy directions has been studied in a magnetite (Fe 3 O 4 ) thin film grown by infrared pulsed-laser deposition on SrTiO 3 (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 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 Fe 3 O 4 thin films by proper control on the growth parameters and substrate choice. The in-plane magnetic easy axis of Fe 3 O 4 film grown on SrTiO 3 :Nb substrate by PLD (nanosecond IR laser) switches with temperature from 〈100〉 (above Verwey transition temperature, T V ) to 〈110〉 ( T < T V ) directions.