Writing bits of longitudinal quantized magnetic disk using magnetic force microscope tip

Longitudinal quantized magnetic disks (QMDs) consisting of discrete single domain Ni bars on a silicon substrate with a density of nearly 2 Gbis/in.² were fabricated. A magnetic force microscope (MFM) tip with a large magnetic moment has been used to successfully write individual bits of the QMD by simply positioning the tip near one end of a Ni bar. It was found that the MFM tip can write each individual bit perfectly without writing the neighboring bits. This is attributed to the fact that the magnetization of each QMD bit has only two stable quantized values and therefore the writing process is quantized.