Magnetic domain structures of multilayered permalloy films observed by spin-polarized SEM.

The domain structures of cores with patterned permalloy films are investigated in order to develop thin film magnetic heads with narrow track widths using spin-polarized SEM. This method made it possible to determine the direction of the magnetization in magnetic cores accurately. For single layered permalloy films, triangular domains are dominant and no 180° walls are observed at pole pieces when the track width becomes less than 10μm. For two layered permalloy films with an alumina interlayer of 4 nm thickness, domain structures show that the direction of the magnetization remains oriented along the track width even at the width of 7μm. Furthermore, for six layered permalloy films with an alumina interlayer of 20 nm thickness, the length of 180° walls at pole pieces becomes longer than two layered permalloy films with an alumina interlayer of 4 nm thickness. It is thus concluded that multilayered permalloy films with single domain structures are most suitable for thin film magnetic heads with narrow track widths.