Spin-polarized scanning tunneling microscopy operating in operating tip magnetization mode

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In order to obtain a high resolution image routinely even in a rough surface of a ferromagnetic sample with a spin-polarized scanning tunneling microscope (SP-STM) operating in modulating tip magnetization mode, we have developed a SP-STM using a micrometer-sized magnetic tip integrated onto a magnetic recording head of a hard disk drive. The tip apex was formed into a round shape of which diameter is less than one micrometer by a focused ion beam instrument. Driving the recording head with a signal generator to switch the magnetization of the tip apex periodically generates unnecessary artificial current flow into a current-to-voltage (IV) converter through a stray capacitance, which prevents to detect the spin-polarized tunneling current precisely. To reduce the artificial current, we added a home-made circuit into the input of the IV converter which generates a countercurrent against the artificial current. We applied the SP-STM to measure the spin-dependent tunneling current of a ferromagnetic polycrystalline film, and also tried to image both the topography and the spin polarization of an iron thin film deposited on a magnetic recording medium whose local roughness is the order of several nanometers due to the crystal grains of the medium. This is the first spin image of the magnetic thin film having such a rough surface with SP-STM.