MEASUREMENT OF POINT CONTACT ANDREEV-REFLECTION CHARACTERISTICS OF HALF-METALLIC THIN FILMS

摘要

An apparatus for measuring spin polarization via Point Contact Andreev Reflection (PCAR) at a magnet-superconductor junction, with variable magnetic fields and temperature control. A cryostat probe investigates superconducting energy gap and Andreev reflection in superconductor-half metal junctions, in a wide range of magnetic fields and temperature form 2K-300K. The cryostat probe is integrated with a commercial physical properties measurement system. The measurement probe includes a rotary-translation stage with coarse and fine screws the tenable a user to make point contacts in a cryogenic, evacuated environment where the point contact junction can be controlled at room temperature by turning a knob. Copper wires are connected as electrical leads from an aluminum housing, descend down to a copper housing for measurement, when contact is made by tip with a half-metal sample, such as CrO2: External current and voltage meters measure the current-voltage characteristics and data acquisition is performed using computer interface.