Combinatorial Hall Effect System for Oxide Films

Combinatorial film growth techniques have made it possible to produce large numbers of high-quality oxide films at one time. Characterizing the samples by traditional methods would be far too slow. Certain measurements, such as the Hall effect, require careful temperature control and lock-in amplifiers to resolve the small signal. We have just built a complete system for measuring the Hall effect in 32 samples simultaneously. The system consists of our home-built, 32-channel lock-in amplifier system, a gas-flow cryostat with a pogo-pin array, a 1 Tesla electromagnet, computerized data acquisition and temperature control, and a specially-built multiplexer to reconfigure the sample leads to allow resistivity measurements. Test show that the system show a good voltage resolution of 15~nV with typical signals of 1~$\mu$V. We hope to show data from a series of La$_{\rm 2-x}$Sr$_{\rm x}$CuO$_{\rm 4}$ samples.