Scanning Hall probe microscopy with shear force distance control

We describe a new type of scanning Hall probe microscope operating at room temperature for quantitative and noninvasive measurements of magnetic stray fields. The probe-sample distance is controlled by piezoelectrical detection of the shear forces acting on an oscillating cantilever. The Hall probes are manufactured from prepatterned GaAs wafers overgrown with a GaAs/AlGaAs heterostructure containing a high-mobility two-dimensional electron gas a few ten nm below the surface. The active Hall area is defined by optical and electron-beam lithography with a junction width of 0.6 μm yielding in a resolution of approximately 0.4 μm. The Hall coefficient of the sensor at room temperature is 0.23 Ω/G with a noise level of ∼0.1 G/Hz^1/2. We show measurements of the stray field pattern of bits written on a magnetic hard disk. © 2000 American Institute of Physics.