Optimization of magnetic properties in fast consolidated SrFe12O19 nanocrystallites

Abstract

The magnetic properties of SrFe₁₂O₁₉ nanocrystallites produced by hydrothermal synthesis and consolidated by Spark Plasma Sintering (SPS) were optimized by varying the compaction parameters: sintering time, sintering temperature, uniaxial pressure or pre-compaction in a magnetic field. Highly textured compacts with a high degree of crystallite alignment were produced. Qualitative and quantitative textural information was obtained based on X-ray diffraction pole figure measurements. The optimum sintering conditions, relating the degree of alignment and bulk magnetic properties, were identified based on the resulting magnetic properties. It was found that one must strike a balance between the degree of crystallite alignment for high saturation magnetisation and coercivity (H_c) to gain the highest energy product (BH_max). It was found that the coercive field drops when the crystallite alignment increases. This was particularly pronounced in the case of magnetically pre-aligned powders prior to SPS, where H_c and BH_max decreased as the pellets became increasingly textured. The best BH_max value of 29(4) kJ m⁻³ was found for the sample sintered at 950 °C for 2 minutes with an applied pressure of 100 MPa for a powder pre-aligned in an applied field of 0.55 T. The results presented here show the potential of SPS consolidation of SrFe₁₂O₁₉ with high relative densities and emphasize the effect of the degree of alignment on the decrease of coercive field and its influence on the magnetic performance.