Zn-Zr induced structural and magnetic changes in strontium hexaferrite system

Abstract

Polycrystalline samples of M-type Strontium hexaferrite having chemical composition SrZnxZrxFe12–2xO19 (with x = 0 and 1 and abbreviated as SFO and SZFO, respectively) were prepared successfully using solid state reaction route. The influence of calcination temperature (900 °C – 1300 °C) on the structural, microstructural, and magnetic properties of the SFO samples was explored. X-ray analysis reveals that the SFO sample is pure over the whole calcination range. The obtained X2 (goodness-of-fit; GoF) values are in the ≈ 1.02 - 1.16 range. At 1300 °C, the SFO sample develops preferred orientations along (006), (008) and (0014) crystallographic planes. The incorporation of preferred orientations leads to an improvement in the value of GoF from ≈ 4.72 to ≈ 1.16 (at 1200 °C). However, no preferred orientations are observed in the SZFO samples. Single phase Rietveld refinement is insufficient to explain the structural data. A four - phase and a three -phase refinement has been observed to be suitable in samples calcined at 1200 °C and 1300 °C, respectively. FESEM micrographs reveal a dramatic change in grain size and shape at 1300 °C in both types of samples. The best of magnetic properties has been observed at 1200 °C calcination in both types of samples. The best Mr, Ms and Hc values have been observed45.36, emu/g, 90.26 emu/g, 5032 Oe (in SFO sample) and 10.39 emu/g, 58.22 emu/g and 1181 Oe (in SZFO sample), respectively. The lower magnetic parameter values of SZFO samples can be attributed to magnetic dilution. Low temperature M-T measurements establishes the absence of magnetic nature of segregated phases in x = 1 sample.