Combined effect of grain size and hematite content on the magnetic properties of SrxBa1-xFe12O19 ceramic powders

Abstract

SrxBa1-xFe12O19 M-type hexaferrites are critical for permanent magnet applications due to their high magnetocrystalline anisotropy and cost-effectiveness. However, secondary phases like α-Fe₂O₃ and uncontrolled grain growth degrade their coercivity (Hc). In this work, SrxBa1-xFe12O19 hexaferrite powders (x = 0.0, 0.5, 1.0) were synthesized via a single-step ceramic route to investigate the interplay between the presence of both hematite and grain size, and magnetic properties. X-ray diffractometry was conducted for phase identification and scanning electron microscopy was performed to study their structure and morphology. Magnetic characterization showed that Hc peaks at intermediate grain sizes (477–590 nm), with SrFe12O19 achieving a coercivity of 4.70 kOe, and an even higher value of 5.09 kOe for the Sr0.5Ba0.5Fe12O19 powders. A phenomenological model incorporating both grain size distribution and hematite effects successfully fitted coercive field trends (R2 =0.7118–0.9435). The single magnetic domain critical grain size in this study about non-compacted M-type hexaferrite powders can be inferred from the fit