Efficient Kerr Microscopy

The performance of magnetic devices correlates with the spatial distribution and time evolution of the magnetization. In recording heads for example, the magnetization components Mx(t), My(t), and Mz(t) are very sensitive to the device boundaries, defects, issues of design and processing, and an applied or internal magnetic field or magnetomotive force. With the increasing difficulty of reliably modeling complex magnetic devices ever decreasing in size, efficient experimental Kerr-effect contrast imaging of M-components becomes more important as aid to progress in fundamental understanding, diagnostics and development. This paper discloses innovations which enable imaging of pure in-plane magnetization sensitive Kerr components devoid of polar Kerr and background signals. For the component sensitive to perpendicular magnetization, a means for calibrating pure polar Kerr contrast relative to the pure in-plane contrast is described. These methods operate without the reliance on changing magnetic state for background subtraction as in earlier methods. They are therefore applicable to imaging the three M-components at different stages of magnetization in recording heads, and in magnetically 'hard' materials, for example amorphous magnets and media for perpendicular magnetic recording.