Magnetic domains in Ni-Mn-Ga martensitic thin films

A series of martensitic Ni₅₂Mn₂₄Ga₂₄ thin films deposited on alumina ceramic substrates has been prepared by using RF (radio-frequency) magnetron sputtering. The film thickness, d, varies from 0.1 to 5.0 μm. Magnetic domain patterns have been imaged by the MFM (magnetic force microscopy) technique. A maze domain structure is found for all studied films. MFM shows a large out-of-plane magnetization component and a rather uniform domain width for each film thickness. The domain width, δ, depends on the film thickness as in the whole studied range of film thickness. This dependence is the expected one for magnetic anisotropy and magnetostatic contributions in a perpendicular magnetic domain configuration. The proportionality coefficient is also consistent with the values of saturation magnetization and magnetic anisotropy determined in the samples.