Room-temperature Ferromagnetism in Zn1−xNixS Diluted Magnetic Semiconducting Nanocrystalline Thin Films

Room-temperature Ferromagnetism in Zn1−xNixS Diluted Magnetic Semiconducting Nanocrystalline Thin Films

This study reports the structure and the magnetic properties of Zn1−xNixS nanocrystalline filmswith Ni composition ratios of 0.05 x 0.2. Thin films of Zn1−xNixS were deposited on Corningglass substrates by using an electron-beam evaporation method. X-ray diffraction patterns revealedsingle- phase films with a cubic zinc-blend-type structure with preferred crystallographic orientationsalong the (111) and the (220) planes. Evidence for the nanocrystalline nature of the films wasobserved from the investigations of the surface morphology by using scanning electron microscopyand atomic force microscopy. Magnetic domains were observed by using magnetic force microscopyat room temperature, indicating the existence of ferromagnetism over the film’s surface. The magneticmeasurements at 5 K revealed a superparamagnetic behavior. However, room-temperatureferromagnetism was observed in all the nanocrystalline Zn1−xNixS films. The saturation magnetizationfor the Zn1−xNixS films was found to increase with increasing dopant concentration (x). Anexchange interaction between local spin-polarized electrons (Ni2+ ions) and conductive electronsaccording to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mechanism is proposed as apossible mechanism for the ferromagnetism. These results show that the Ni-doped ZnS nanocrystallinefilms are promising materials for applications in spintronic and magnetic sensor devices.

This study reports the structure and the magnetic properties of Zn1−xNixS nanocrystalline filmswith Ni composition ratios of 0.05 x 0.2. Thin films of Zn1−xNixS were deposited on Corningglass substrates by using an electron-beam evaporation method. X-ray diffraction patterns revealedsingle- phase films with a cubic zinc-blend-type structure with preferred crystallographic orientationsalong the (111) and the (220) planes. Evidence for the nanocrystalline nature of the films wasobserved from the investigations of the surface morphology by using scanning electron microscopyand atomic force microscopy. Magnetic domains were observed by using magnetic force microscopyat room temperature, indicating the existence of ferromagnetism over the film’s surface. The magneticmeasurements at 5 K revealed a superparamagnetic behavior. However, room-temperatureferromagnetism was observed in all the nanocrystalline Zn1−xNixS films. The saturation magnetizationfor the Zn1−xNixS films was found to increase with increasing dopant concentration (x). Anexchange interaction between local spin-polarized electrons (Ni2+ ions) and conductive electronsaccording to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction mechanism is proposed as apossible mechanism for the ferromagnetism. These results show that the Ni-doped ZnS nanocrystallinefilms are promising materials for applications in spintronic and magnetic sensor devices.