Development of measuring method for the three-dimensional high frequency micro-magnetic stray fields extending beyond a magnetic head by reflection electron tomography

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A new method for measuring the three-dimensional high frequency micro-magnetic stray fields extending beyond a magnetic head by reflection electron tomography are developed. This method is based on tomographic technique, in which the magnetic fields are reconstructed from the deflection vectors of the electron beams deflected by the Lorentz force when traversing through magnetic fields. In this method, the electron beams are injected at right angles to the surface of a specimen, while scanning their injection positions regularly, and the resulting deflection vectors of the electron beams traversing through the magnetic fields and being reflected from the surface of the specimen are measured. From these data, the three-dimensional magnetic stray fields extending over in this region are iteratively reconstructed by an ART method (Algebraic Reconstruction Technique) using the BEM (Boundary Element Method) for calculating the magnetic field distribution. Our proposed method is tested with a known magnetic field model of one-turn coil by computer simulation.It is shown numerically that the field distribution just beyond the specimen can be evaluated three dimensional with an error of around 20 %. And from these experimental results, it is confirmed that our method can be applicable to the measurement of micro-magnetic stray fields just beyond the gap region.