Enhanced magnetic properties of strontium ferrites through constructing magnetoelastic stress

Strontium ferrites, which exhibit large remanence, high coercivity (Hc), are fascinating for applications in motors and high-frequency microwave devices. Here we demonstrate the strontium ferrites (Sr0.34Ca0.25La0.41Fe11.4Co0.19O19-δ) sintered at 1150 °C with enhanced magnetic properties through constructing magnetoelastic stress. The effects of applied pressure (Pc-axis) of 0–16 kPa during the sintering process on phase compositions, morphologies, magnetic and microwave properties are investigated in detail. We note that the Pc-axis could contribute to enhanced c-axis preferred orientation. This mechanism of enhancement has been also discussed according to the magnetoelastic theory. By applying an external pressure of 8 kPa, intrinsic coercivity (Hcj) of 4657 Oe and magnetic coercivity (Hcb) of 3781 Oe are obtained. The increments are 8.1% and 18.0% for Hcj and Hcb, respectively, compared to the sample with Pc-axis of 0 kPa. However, the enhancement of Hc by the Pc-axis is seen to be limited above 8 kPa, which can be attributed to the enlarged grain size and porosity observed. In addition, the ferromagnetic resonance frequency (fr) is also increased by the increased Pc-axis.