Direct Measurement of the Magnetic Cluster Size Using High-Resolution Magnetic Force Microscopy

High-resolution magnetic force microscopy was used to image high linear density tracks and measure the magnetic cluster size of the ac-erased state of perpendicular magnetic recording media. The full-width at half-maximum (FWHM) of the auto-correlation function corresponding to an ac-erased region determines the correlation length, i.e., the magnetic cluster size. This is demonstrated by comparing the calculated FWHM of auto-correlation function obtained on simulated Voronoi granular structures with the expected value for magnetically decoupled grains. The cluster size we obtained using the auto-correlation procedure is about four grain sizes. The impact of the finite cluster size on the recording performance was assessed by following the trend of tracks' auto-correlation function with increasing the linear density.