Structural, electrical and magnetoresistance of titanium-doped iron (II,III) oxide (Fe_3O_4) thin films deposited on strontium titanate, alumina, silicon, and Float Glass

摘要

Titanium (Ti) doping effects on the structural and transport properties of half-metallic Fe_3O_4 iron (II,III) oxide (magnetite-Fe_3O_4) films grown on various substrates such as strontium titanate (SrTiO_3 (100)), silicon (Si (111)), alumina (Al_2O_3 (0001)), and Float Glass (FG) by pulsed-laser deposition (PLD) are studied. X-ray diffraction (XRD) pattern infers that parent and Ti doped magnetites have cubic spinel structure. The first order phase transformations at the Verwey transition T_v for Fe_3O_4 thin films are 123 K (SrTiO_3), 120 K (Si), 123 K (Al_2O_3), and 121 K (Float Glass). Raman spectra infer five Raman-active modes (A_(1g), Eg and three T_(2g) modes) and gradual changes are evident on Ti doped films on different substrates. Magnetoresistance (MR) curves show linear magnetic field dependence for the parent films, while an increase in MR and departure from linear field dependence is observed for Ti-doped films. MR curves display highest change for doped and undoped films grown on Al_2O_3 (0001) substrate. For parent Fe_3O_4 films MR is of-0.48% at room temperature which increases below the Verwey transition up to-1.12% at 100 K, while in Ti doped films MR is of-1.56% at room temperature which increases up to-3%.