A scanning Hall probe microscope for large area magnetic imaging down to cryogenic temperatures

We describe the design, construction, and operation of a large area scanning Hall probe microscope that is built around a closed-cycle refrigerator capable of cooling samples down to 35 K. The system operates in a custom vacuum housing that utilizes a flexible vacuum bellows to link to external stepping motor positioning stages allowing x–y scans of 5 mm×5 mm under vacuum at 35 K, increasing to 25 mm×25 mm in atmospheric pressure at 300 K and in magnetic fields up to 0.06 T. The Hall probe can be viewed with a microscope through a window and lowered to the desired scanning height and tilted with micrometer screws. The system has an effective lateral spatial resolution of 1.25 μm and a minimum detectable field of ∼0.08 μT/√Hz. We describe the performance of the system and illustrate its potential with images of the local magnetic induction at the surface of various magnetic recording media at room temperature as well as an array of superconducting YBa2Cu3O7−δ squares at 40 K.