Influence of 190 MeV Ag ion irradiation on structural and magnetic properties and oxygen content of NiMn0.05TixMgxFe1.95-2xO4 (x 0.0, 0.2) ferrite thin film

We present the studies on the swift heavy ions (SHI) irradiation induced modifications in structural and magnetic properties of NiMn0.05TixMgxFe1.95-2xO4 for x=0.0 and 0.2 thin films grown by rf magnetron sputtering. We also present the effect of irradiation on the oxygen content of the thin films. X-ray diffraction (XRD) patterns of the as-deposited films reveal the spinel structure of the films. These ferrite films were irradiated with 190 MeV Ag ion for fluence range from 5 x 1010 to 1 x 1012 ions/cm2. The XRD pattern of the irradiated films shows strain-induced texture effect i.e. the spinel peaks get textured along (1 1 1) plane, whereas the (3 1 1) peak, which was the major peak with maximum intensity in the spinel ferrite, vanishes after irradiation. The XRD peaks in case of irradiated NiMn0.05Fe1.95O4 film were of very low intensity; however, the peak intensities of irradiated NiMn0.05Ti0.2Mg0.2Fe1.55O4 film were of high intensity up to 1 x 1011 ions/cm2 as compared to the pristine film. From the DC magnetization measurements, it has been observed that the saturation magnetization (Ms) decreases for NiMn0.05Fe1.95O4, whereas it increases for NiMn0.05 Ti0.2Mg0.2Fe1.55O4 thin film with ion fluence. The maximum Ms was observed for NiMn0.05Ti0.2Mg0.2Fe1.55O4 thin film irradiated with 1 x 1011 ions/cm2 and with further increase in ion fluence the magnetization decreased. The enhancement in the saturation magnetization of irradiated films may be due to the ion induced texturing of the films along (1 1 1) plane (an easy axis of spinel ferrite). Variation in the oxygen content on irradiation can affect the interatomic distance that can lead to change in the magnetic interaction. Therefore, to measure the oxygen content in the thin film on irradiation, Elastic recoil detection analysis (ERDA) studies have been performed. From the ERDA results, it is evident that the oxygen content in the samples remains same even up to the fluence value 1.52 x 1013 ions/cm2