The Application Of Magnetic Force Microscopy In The Study Of Nanomagnetic Thin Film Magnetic Domains

In this paper, the using of Magnetic Force Microscopic (MFM) was introduced andthe transformations of magnetic domains were investigated by MFM.The influences of the magnetic tip on domain images have been studied and themethods of avoiding the influences it have been introduced. Based on the former work,the influences of the film thickness, the working pressure, the external stress and theremanent magnetization on the domain structures of the Co₆₀Fe₂₀B₂₀, Co_9.8Fe₈₁Si₇B_2.2and CoFeO magnetic film materials have been studied by MFM.The thickness dependent domains structures of Co₆₀Fe₂₀B₂₀, soft magnetic thin filmhave been investigated. Results show that, at room temperature a dependence ofperpendicular magnetic anisotropy on thickness is observed .Magnetic domain sizesdecrease initially with the increase of the film thickness (2.5nm-20nm). With the furtherincrease of the film thickness (20nm-400nm), the domain sizes increases. The minimumof domain size is reached at the thickness of about 20nm.The working pressure dependent domains structures of amorphous Co_9.8Fe₈₁Si₇B_2.2,magnetic thin film have been investigated. The surface topography and component offilms change with the working pressure. Results showed that, when working pressure issmaller than 2.5pa, domain structure is more influenced by surface topography; whenworking pressure is above 2.5pa, domain structure is more influenced by component offilms. This phenomenon can be explained by the losing of Co and Fe in theCo_9.8Fe₈₁Si₇B_2.2 material with the increase of the working pressure.The effects of tensile stress and compressive stress on the domain structures of theamorphous Co_9.8Fe₈₁Si₇B_2.2 thin films have been studied. MFM images show that,whether tensile stress or compressive stress, the domain size increase with the increaseof the stress strength, As the stress strength increases further, there is no obvious colorcontrast in the images. This can be explained by the fact that, magnetization directionturned parallel to the film plane. In this case, the easy magnetization direction willparallel to stress vector when tensile stress is applied and perpendicular to stress vectorwhen compressive stress is applied. The influences of remanent magnetization on domain structures have been studiedin the CoFe₂O₄ magnetic thin film material. The influences of remanent magnetizationare caused by the movements of domain walls and the rotations of domains. Resultsshow that, with the movements of domain walls, dot domains transform into netdomains and some domain walls inosculate. With the increasing of remanentmagnetization, the domains rotate and the size of single dot domain increase. When theexternal magnetization is above 15kOe, the domain structure does not transform anymore. This is due to the saturation of the remanent magnetization.