Influence of the substrate and precursor on the magnetic and magneto-transport properties in magnetite films

Abstract: We have investigated the magnetic and transport properties of nanoscaled Fe3O4 films obtained from Chemical Vapor Deposition (CVD) technique using [FeIIFe2III(OBut)8] and [Fe2III(OBut)6] precursors. Samples were deposited on different substrates (i.e., MgO (001), MgAl2O4 (001) and Al2O3 (0001)) with thicknesses varying from 50 to 350 nm. Atomic Force Microscopy analysis indicated a granular nature of the samples, irrespective of the synthesis conditions (precursor and deposition temperature, Tpre) and substrate. Despite the similar morphology of the films, magnetic and transport properties were found to depend on the precursor used for deposition. Using [FeIIFe2III(OBut)8] as precursor resulted in lower resistivity, higher MS and a sharper magnetization decrease at the Verwey transition (TV). The temperature dependence of resistivity was found to depend on the precursor and Tpre. We found that the transport is dominated by the density of antiferromagnetic antiphase boundaries (AF-APB's) when [FeIIFe2III(OBut)8] precursor and Tpre = 363 K are used. On the other hand, grain boundary-scattering seems to be the main mechanism when [Fe2III(OBut)6] is used. The Magnetoresistance (MR(H)) displayed an approximate linear behavior in the high field regime (H > 796 kA/m), with a maximum value at room-temperature of \sim2-3% for H = 1592 kA/m, irrespective from the transport mechanism.