Micromagnetic models of the effect of particle shape on magnetic hysteresis

Direct calibration of magnetic hysteresis with grain size is of particular interest for submicron particles. In the present study, we numerically tested the effect of particle shape (grain morphology and aspect ratio) on magnetic hysteresis of stress-free Fe3O4. We found that the particle shape has a profound effect on hysteresis behavior. In particular, for particles with grain width >120 nm, octahedra (and tetragonally terminated prisms) showed higher coercivity and squareness than cubes (and rectangular parallelepipeds) due to an inherent geometric advantage. The results from micromagnetic calculations and experimental observations are somewhat mismatching. It is likely that stress-free Fe3O4 used in hysteresis experiments were not entirely stress-free or the grain size of stress-free Fe3O4 was overestimated on using two-dimensional images of three-dimensional objects.