Reconstruction of magnetic fields by reflection electron tomography

The trend in magnetic record development is toward ever higher areal storage density. Methods for accurate measurement of the magnetic field distribution iri the very small region surrounding the gap of the recording head have been the focus of several recent studies. Using transmission electron beam tomography, a new reconstruction technique is proposed and applied to measure three-dimensional magnetic stray field extending beyond a commercial magnetic head by a developed measurement system. Results have demonstrated the applicability of this technique for measuring a magnetic stray field of several kGauss with an error of less than 10 percent. With transmission electron beam tomography, however, it is difficult to measure directly the magnetic field just beyond the gap of a magnetic head. This is because the stronger Lorentz force of the magnetic field on the electron beam causes the election beam to collide with the head surface. A new method, called reflection electron beam tomography, is presented herein to overcome the forementioned limitation in which the electron beams are injected perpendicularly to the surface of a magnetic head and their deflection vectors are measured at the deflection plane set above the head. Our method is tested with a known magnetic field model of a one-turn coil by computer simulation. Results have shown that the magnetic field just beyond the gap of the magnetic head can be estimated with an error of approximately 20 percent.