| A design is presented for a point-contact Andreev reflectivity spectroscopy (PCARS) probe for measuring the degree of spin polarization of bulk and thin film materials. The probe was designed to be inserted into a standard 100 liter liquid helium dewar, and to operate at one temperature (4.2 Kelvin). The source and measurement electronics were interfaced to a computer system and software was developed to collect, store, and analyze the data. Niobium tips were fabricated using an electrochemical etching technique, and optimized etching parameters have been determined. An algorithm based on a modified Blonder-Tinkham-Klapwijk (BTK) theory was developed to compare the theory to current-voltage measurements. Data for Cu and NiFe were analyzed using the modified BTK algorithm in order to demonstrate proof of concept for this PCARS system. Suggested improvements are given for the next generation PCARS probe. |
