Abstract
Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.
Highlights
Fe1.5Ti0.5O3−δ (FTO) is a mixed valence transition metal oxide based on the solid solution of hematite (Fe2O3) and ilmenite (FeTiO3)
New interest occurred for this material in thin films due to its potentiality for spintronics applications, which require a combination of room temperature ferromagnetic properties and spin polarized conductivity [3]-[7]
Before analysing the electrical transport and magneto-transport properties of FTO, macroscopic magnetization measurements of the films have been performed in two magnetic field directions: perpendicular and parallel to the film plane
Summary
Fe1.5Ti0.5O3−δ (FTO) is a mixed valence transition metal oxide based on the solid solution of hematite (Fe2O3) and ilmenite (FeTiO3). While in the case of R(-3)c disordered symmetry, titanium atoms are randomly distributed on the cation sites. This atomic scaled Ti/Fe order along the c-direction strongly influences the macroscopic magnetization of FTO thin films as it demonstrates the significantly larger macroscopic magnetization in ordered phase in disordered one [4] [5]. The influence of this atomic scaled “order-disorder” on the electrical properties (conductivity, magneto-resistance) of FTO was not studied in detail. One report is claiming that conductivity in zero magnetic field does not depend on cation order [4]
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