Effect of intragranular exchange on exchange-coupled composite media

A micromagnetic approach was adopted to study the effect of the intragranular exchange parameter, A(ergs∕cm), on the switching of exchange-coupled composite (ECC) media. A single grain of ECC media was simulated by subdividing it into small cubes and introducing appropriate exchange within different regions of the grain. We find full coupling between the hard and soft regions to be necessary to facilitate switching of a hard region with very high anisotropy, Ku(∼2×107ergs∕cm3). This method also allows for rotation mechanism analysis within the ECC grain. We report nonuniform rotation that is observed as a domain nucleating in the bottom region of the soft part and moving its way up to and through the hard/soft layer interface, if the intragranular exchange coupling is appropriate. Field sweep-time analysis revealed that ECC media was capable of following the rapidly changing field more efficiently than regular perpendicular media.