Nanocrystalline magnetite thin films grown by dual ion-beam sputtering

We have explored the influence of an ion-assisted beam in the thermoelectric and magnetic properties of nanocrystalline magnetite thin films grown by ion-beam sputtering. The microstructure has been investigated by XRD. Tensile and compressive strained thin films have been obtained as a function of the parameters of the ion-assisted beam. The evolution of the in-plane magnetic anisotropy was attributed to crystalline grain size. In some films, magneto-optical Kerr effect measurements reveal the existence of uniaxial magnetic anisotropy induced by the deposition process related with a small grain size (<= 20 nm). Isotropic magnetic properties have observed in nanocrystalline magnetite thin film having larger grain sizes. The largest power factor of all the films prepared (0.47 mu W/K-2 cm), obtained from a Seebeck coefficient of -80 mu V/K and an electrical resistivity of 13 m Omega cm, is obtained in a nanocrystalline magnetite thin film with an expanded out-of-plane lattice and with a grain size approximate to 30 nm. (C) 2015 Elsevier B.V. All rights reserved.