Magnetic domain walls in thin films of nickel and cobalt

Abstract

The method of observing magnetic domain walls in thin films of ferromagnetic metals by out-of-focus transmission electron microscopy has been applied to films prepared from bulk material by electropolishing. It proved possible to study both domain walls and imperfections simultaneously in both nickel and cobalt. In nickel, no obvious dependence on orientation or foil thickness was found, as expected for a material of such low magneto-crystalline anisotropy. In cobalt, the domain walls were found to lie along the traces of the [0001] direction, the easy axis, in the foil plane and marked changes in structure were noted at grain boundaries as expected for a metal of high magneto-crystalline anisotropy. It also proved possible to move the domain walls in a relatively controlled manner by the application of a small magnetic field. While pinning at holes during movement was observed in both nickel and cobalt, no marked effect was noted at dislocations.