Platelet-like hexagonal SrFe12O19 particles: Hydrothermal synthesis and their orientation in a magnetic field

• We prepared platelet-like hexagonal SrFe12O19 particles by hydrothermal synthesis.
• The platelet-like particles arrange with the platelet perpendicular to the magnetic field direction.
• The magnetocrystalline anisotropy plays a leading role in the changing effective anisotropy with the rapidly growing shape anisotropy.
• The SrFe12O19 (BH)max can be effectively adjusted after magnetic orientation.

Platelet-like hexagonal SrFe12O19 particles were prepared by hydrothermal synthesis, and the effects of molar ratio of Fe/Sr (RFe/Sr) on the phase compositions, morphologies and magnetic properties of as-prepared samples were investigated. The optimum RFe/Sr is identified as 8:1. The hexagonal platelet-like particles are nano-scale in thickness and micro-scale in diameter. The low coercivity is a consequence of the large shape anisotropy of the as-synthesized particles.The platelet-like hexagonal SrFe12O19 particles were then dispersed in epoxy resin and formed ordered arrangement structure which took root in the curing epoxy matrix under an external magnetic field of 8000 Oe. The microstructures, morphologies and magnetic properties of the bulk samples orientated and nonaligned were studied. The platelet-like particles arrange with the platelet perpendicular to the magnetic field direction in the orientated samples. This demonstrates that the easy axis of the particle is perpendicular to the platelet, and that the magnetocrystalline anisotropy still plays a leading role in the changing effective anisotropy with the rapidly growing shape anisotropy. The remanence (Mr) of the bulk samples is changed obviously after orientation, while the coercivity nearly remains constant. That is, the maximum energy products (BH)max can be effectively adjusted by given a suitable magnetic field.