Inter-particle interaction and thermal stability of ultra-fine Ba ferrite particles for high-density recording

Abstract Newly developed ultra-fine Ba ferrite particles, having the mean diameters of 21.9–41.5 nm, were used to prepare encapsulated powder samples and sheet samples. The powder samples and non-oriented sheet samples exhibited almost zero amplitude in ΔM peaks; however, the longitudinally oriented sheet samples showed positive ΔM peaks, implying that positive interaction acts among particles. It was clarified that this positive interaction accelerates magnetization time decay, when the applied reverse field is greater than some fraction of Hc, but it suppresses the time decay when the reverse field is smaller than the value. The magnetization time decay in the presence of a large reverse field was noticeable when particle diameters were