Effect of lattice mismatch on magnetic properties of acicular spinel iron oxide particles with crystallized cobalt ferrite layer

Cobalt ferrite was epitaxially crystallized on acicular seed iron oxide particles with different lattice constants and same particle shape to analyze the effect of the lattice mismatch on magnetic properties. The coercive force obtained by crystallizing 27 vol% of cobalt ferrite was approximately 530-640 kA/m, which tended to increase with the decrease in the difference of lattice constants between the seed particles and cobalt ferrite, which is different from the results for thin films. The obtained coercive force was higher than that considering the contribution of anisotropy from the cobalt ferrite crystallized on the seed particles. In the acicular iron oxide spinel particles, the epitaxial growth of cobalt ferrite was considered likely to occur with a smaller difference in the lattice constants of the seed particles and cobalt ferrite. The high coercive force of the cobalt ferrite crystallized iron oxide particles strongly suggested the influence of exchange coupling between the seed iron oxide particles and cobalt ferrite layer.