"Lorentz" microscopy of stripe domain films with protons

A new method is reported for observing the in-plane component of magnetic structure in stripe domain films. Stripe domain films act as a Faraday-effect diffraction grating, and deflect light beams in a way reminiscent of electrons being deflected by the Lorentz force in a magnetic thin film. The direction of the stripes is that of the local in-plane magnetization vector. Thus the angle of deflection is perpendicular to the local in-plane magnetization, as is the case for Lorentz deflection. Micrographs are presented demonstrating that with a displaced aperture one can perform with light the analogues of the two modes of Lorentz microscopy: light-field microscopy in the defocused mode and dark-field microscopy with light normal to the film plane. In the defocused mode, walls appear as either bright streaks or dark streaks; if one focuses on the opposite side of the film the bright walls become dark and vice-versa. In the dark-field mode the contrast of the dark regions and the bright regions can be reversed by moving the aperture.