Differential type Scanning Hall probe microscopy with high resolution of magnetic field image

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A scanning Hall probe microscope, which can be used in external magnetic fields below 15 kOe in the temperature range from 20 K to 300K, is developed. The surface magnetic images are measured as a function external magnetic field perpendicular to a ferromagnetic film plane, and the stray-magnetic-field images above the film are obtained by subtracting the external magnetic filed contributions.A scanning probe and stage are installed in a cryostat which is set in the gap of an electromagnet generating magnetic fields up to 15 kOe. The scanning stage is made of non-magnetic stainless and sapphire ball bearing in order to avoid magnetostriction of the scanning devices. The stage is controlled by stepping motors and piezo actuators which are placed outside the cryostat and flee from the applied magnetic field. The active scanning area is 2mm x 2mm and the spatial resolution is 0.5μgm.A Si-MOSFET micro-Hall probe (SHPM), which is more durable than conventional GaAs/AlGaAs probe, was developed. The Hall coefficient of the Si-MOSFET probe, is 0.18 Ω/G at room temperature, being adequate to use in the SHPM developed in the present study.