Magnetic domain structure in Ni53.6Mn23.4Ga23.0 shape memory alloy films studied by electron holography and Lorentz microscopy

Magnetic domain structure in Ni53.6Mn23.4Ga23.0 films containing nonmagnetic MnO precipitates was examined by electron holography and Lorentz microscopy. Close experiments discovered peculiar zig-zag-shaped lines of magnetic flux, which are presumably typical configuration in the martensite accompanied by many twin plates. Near the edge of the films, this configuration was modified into a distinct form that was favorable to the reduction of magnetic charges. Inside the martensite plates as crystallographic domains, the lines of magnetic flux were wavy due to the electromagnetic interaction with the nonmagnetic MnO precipitates. The observations have promoted an understanding of the magnetic domain structure in ferromagnetic shape memory alloy films, and also provided essential information for developments of magnetic field-driven microactuators using these films