Magnetic contrast in the scanning electron microscope with particular reference to bubble domain structures

A study has been made of the usefulness of the SEM for the observation of magnetic bubble-like domain structures in a variety of oxide materials. The basic theory behind the technique is outlined including a rigorous evaluation of the fiekd integral for an isolated bubble and a hexagonal bubble lattice. Secondary electron trajectories have been computed and give reasonable agreement with those predicted from the model used.Experimentally it has proved possible to observe magnetic bubbles in garnet but the contrast is generally poor. Better results are obtained in hexa- and ortho-ferrites including the resolution of surface detail. The possibility of scanning electron optical detection in a bubble memory is discussed but the signal-to-noise ratio is again unfavourable for garnets.