Scanning Hall Probe Microscopy with Shear Force Distance Control

Abstract

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 /G with a noise level of 0.1 G/Hz1/2. We show measurements of the stray field pattern of bits written on a magnetic hard disk.