Magnetic behaviour of Fe-doped CdS diluted magnetic semiconducting nanocrystalline thin films

Abstract

We have investigated the magnetic properties of Fe doped Cd1−xFexS diluted magnetic semiconducting nanocrystalline thin films for different doping concentrations (0.05 ≤ x ≤ 0.2) synthesized by electron beam evaporation technique. X-ray diffraction patterns confirm the existence of single phase nature in all the Fe doped Cd1−xFexS samples with hexagonal wurtzite type structure with a strong (002) preferred orientation. Evidence of nanocrystalline nature of the films was observed from the investigation of surface morphology using scanning electron microscopy and atomic force microscopy. Magnetic domains were observed by using magnetic force microscopy at room temperature indicating the existence of ferromagnetism over the film surface. The temperature and field dependent magnetization measurements by using superconducting quantum interference device showed ferromagnetic behavior between room temperature and low temperature (5 K) with a Tc at or above room temperature for the nanostructure samples with 0.1 ≤ x ≤ 0.2. The saturation magnetization for Cd1−xFexS system is found to increase with the dopant concentration (x). The exchange interaction between local spin polarized electrons (Fe3+ ions) and conductive electrons according to Ruderman-Kittel-Kasuya-Yosida mechanism, rather than from the Fe oxide impurities, is proposed to be the possible mechanism for ferromagnetism. These results show that the Fe-doped CdS nanocrystalline films can be employed in the fabrication of the nanoscale magnetic device.