The Design and Test of an STM-MFM Microscope Combo for Use in a $\Phi$ 52 mm 18/20 T Superconducting Magnet

We present a novel scanning-tunneling-microscope (STM) and magnetic-force-microscope (MFM) combo (SMC) system, which is for using in a commercial Oxford 52 mm cold bore 18/20 T superconducting magnet. There are three design highlights: (1) An unique vacuum chamber consisting of two lengths of pipe: a long outer diameter (OD) 19 mm pipe and a short OD 50 mm capped-off pipe that are knife-edge press sealed together by two half-cylindrical clamps without diameter expansion (still fits the ¿52 mm bore). (2) A compact SMC head, in which a pillar and a piezoelectric tube scanner (S1) are mounted in parallel with one ball glued on the pillar top and two balls glued on the scanner top. The three triangularly arranged balls support a triangular slider piece. Additional two scanners standing underneath the slider scan the STM and MFM tips respectively. By inertial stepping, the scanner S1 can move the slider toward the pillar (coarse approach) or rotate the slider about the pillar (change scanning tips). (3) A design in integrating complicated instruments into small bore magnet while still keeping high-field compatibility. The objective of the SMC, its progress and the test results are also described in this paper.