Study on magnetic and electric properties of 4d transition metal-doped oxide films

Abstract

We have investigated magnetic properties of molybdenum-doped ( 0 ~ 10 at %) indium oxide (IO) films. The films were prepared on (100) MgO substrates at 450 °C using a pulsed laser deposition (PLD) technique in a high vacuum chamber with a base pressure of 3 utorr. Targets of undoped (99.99 % purity) and 3 % and 5 % Mo-doped (99.95 % purity) In2O3 were used to prepare the films. The targets were ablated with or without an oxygen environment using a KrF excimer laser (λ = 248 nm) operating at 2 Hz with an integrated intensity of 0.3 J/cm2. The target was rotated during deposition to reduce particulate formation. A typical deposition rate was ~0.5 Å/s. The structures of the films were characterized by θ-2θ x-ray diffraction (XRD) using a 12 kW Rigaku diffractometer (model D/MAX-RC). Rutherford back scattering (RBS) measurements were carried out to detect the possible existence of magnetic impurities as well as to determine the In and Mo composition ratio. The mag-netic properties were investigated using an alternating gradient magnetometer. We have also carried out magnetoresistance (MR) measurements to investigate any spin-dependent transport behavior. Additionally R-T(resistance versus temperature) and Hall effect measurements have been carried out to investigate the correla-tion between magnetism and electric conductivities. The films were found to reveal room-temperature ferromagnetism, where the magnetization was increased with Mo doping. The saturation magnetization became 6.6 emu/cc for the 5% Mo-doped IO, resulting in about 5 times enhancement in comparison to the undoped film. And we have investigated the correlation between the ferromagnetism and electric conductivity of Mo-doped (3 ~ 10 at%) In2O3 films. It is believed that the enhance-ment in the magnetization is ascribed to the magnetic moments of Mo ions occupied in the In sites. We found that the saturation magnetization increases with Mo concentrations until it reaches the maximum at 7 at% Mo dop...