Measurement of the three-dimensional high frequency micro-magnetic stray fields beyond a magnetic head by electron tomography

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A new measuring system by reflection electron beam tomography has been developed to measure the stray magnetic fields of a magnetic head with gap length of 1 μm and under. We developed the measuring system to measure the magnetic stray fields of the magnetic head with gap length of 10 μm and over by reflection electron beam tomography, but it is difficult to measure the magnetic fields of a magnetic head for the high density magnetic record.In this study, in order to improve the measurement accuracy of deflection data of electron beams deflected by the objected magnetic fields, a high accurate commercial type PSD (Position Sensing Detector) is introduced and its performance was studied experimentally. First, to improve the S/N ratio of the PSD, the parameter value of the feedback resistance in the current - voltage transform circuit was adjusted. Second, to obtain the good linearity of position detection of the electron beam, the incident current of electron beams onto the PSD is increased by changing the aperture size of the object lens and also increasing the excitation current of the condenser lens of the SEM. Unfortunately, though these modifications were done, the spatial resolute of the PSD was around 25 μm and can not be improved due to the resulting increment of the radius of the electron probe beams by changing the aperture size of the object lens. Finally, the sample stage for holding the magnetic head was modified to improve the reproduced accuracy of the decision of the stage. From these modifications, it is expected to measure the stray magnetic fields of a magnetic head with gap length of 1 μm and under for the high density magnetic record.