Signal enhancement of 0.2 μm packed domain in magnetic domain expansion readout disk with gating layer

Magnetic domain expansion readout under the condition of no alternative magnetic field are studied. The reproduced waveform of a 0.2 μm domain has a very sharp shape and large amplitude of 70% to the saturated signal level. It is found that the linearity of the readout signal including domain expansion phenomenon is maintained as well as a conventional readout, therefore relatively clear reproduced signal of the 0.2 μm packed domain can be detected. In order to improve it, the sharper readout waveform must be reproduced by using a gating layer between the expansion and the recording layers, and the readout signal of the 0.2 μm packed domain is enlarged two times relative to that without a gating layer