Magnetic and magnetization properties of iron oxide thin films by microwave assisted sol–gel route

Abstract

Iron oxide thin films have attracted worldwide attraction due to their technological importance in magnetic tunnel junctions, recording media, as a catalyst etc. However, the use of microwave energy for obtaining crystallinity and phase transition in the form of thin films has long being neglected. We here report preparation of iron oxide thin films using microwave energy instead of conventional heating methods during sol–gel synthesis. The solution was subjected to microwave radiations, for sol synthesis, with variation in microwave power. The maximum power used in this study is 800 W with variation in power as 136, 264, 440, 616 and 800 W. These are among the lowest powers applied for synthesis of iron oxide sol. XRD, FTIR and VSM results indicate that use of microwaves can lead to enhanced crystallinity and phase stability, thus enhancing the magnetic properties with variation in power of the incident microwaves. At low power of microwaves mixed phases of iron oxide exist whereas with increased power up to 616 W pure maghemite phase was obtained. Further increasing the microwave power to 800 W, results in formation of pure magnetite phase. FTIR bands at 477 and 550 cm−1 indicate formation of pure magnetite phase. The films exhibit ferromagnetic behaviour with saturation magnetization of 453 emu/cm3. Verwey transition, determined using low temperature electrical properties, reveals sharp reduction in resistivity at a temperature of 125 K.