Magnetic constrast in reflection electron microscopy

The possibility of obtaining magnetic contrast in reflection electron microscope images is considered. We consider the problem of observing two-dimensional magnetic domains in Fe monolayer films on a GaAs substrate. By introducing the vector potential into multiple scattering RHEED calculations based on the multi-slice algorithm, the effect of the Lorentz force on diffraction conditions is evaluated at the specular condition for 120 kV electrons. This provides a contrast mechanism. For Fe(110)/GaAs(110) the contrast which results in the (440) specular beam from a reversal of B normal to the beam in the plane of the surface is found to be about 28%, suggesting that useful contrast might be obtained from a single monolayer. The penetration depth of the wavefield into the crystal is studied as a function of incident beam direction The distance along the beam path needed to re-establish the steady-state condition following a reversal of B is used to estimate the resolution of the method. The method, which would allow real-time image recording at high sample temperatures, is compared briefly with other magnetically sensitive surface imaging techniques.