Impact of particle size on room temperature ferrimagnetism of SrFe ₁₂O ₁₉

In this paper, we report the control of important hysteresis parameters, which are useful for memory devices, viz. M _s, H _c and M _r/M _s, by changing the particle size/calcination temperature. An investigation of SrFe ₁₂O ₁₉ nanopowder from the structural and magnetic aspect is performed using X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM). The average particle size (APS) of SrFe ₁₂O ₁₉(nanopowder) increases from 26 to 600 nm with calcination temperatures of 400 and 1100 °C in air, respectively. With the increase in calcination temperature, saturation magnetization (M _s) increases with the decrease in coercivity for the respective sample. The change in saturation magnetization and coercive field are explained on the basis of transition from single domain structure to multi-domain geometry with an increase in the heating temperature. The sample heated at 1000 °C shows a minimum coercive field (2.71 kOe) and an appropriate squareness ratio (M _r/M _s) compared to other calcined samples.