Magnetic structures in Co-Cr media for perpendicular magnetic recording

High bit densities have been demonstrated in longitudinal as well as in perpendicular magnetic recording. For the latter an area density of more than 12 G b i t / i n 2 has been obtained in a sputtered C o C r T a hard disk with a soft magnetic underlayer recorded with a special single pole head. In this paper the role of microstructure and morphology in relation to the compositional separation is discussed. Very sensitive anomalous Hall measurements have been performed from submicron C o C r samples to obtain more detail information about the reversal characteristics of the material. The results obtained have been used in our model for micromagnetic simulations. One of the conclusions is that most of the magnetic entities reversing their magnetisations are much smaller than the volume of one C o C r column.