Method for investigating the reversal properties of isolated barium ferrite fine particles utilizing magnetic force microscopy (MFM)

Abstract

The reversal properties of isolated barium ferrite recording particles with Co-Ti substitution (BaFe12−2xCoxTixO19) are studied by a newly developed magnetic force microscopy (MFM)-based technique. The size dependence of the switching field on particles with diameters ranging from 30 to 80 nm were investigated. A decrease in the switching field was observed, which corresponds to a decrease in the particle diameter below 50 nm. This indicates thermally assisted switching in small size particles. As the diameter increases, the switching field reaches a maximum at 55 nm then sharply decreases. An atomic force microscopy (AFM) profile of the particle’s thickness shows that the aspect ratio variation among these particles cannot account for the observed difference in the switching field. Thus, it is concluded that incoherent reversal is occurring in particles with diameter greater than 60 nm.