A CONTACTLESS VIBRATING SAMPLE TECHNIQUE FOR THE MEASUREMENT OF NORMAL-STATE RESISTIVITY, AC SUSCEPTIBILITY AND MAGNETIZATION OF SINGLE-CRYSTALS OF HIGH-TC SUPERCONDUCTORS

The technique relies on a measurement of the out-of-balance signal from an AC (5-100 kHz) bridge, one arm of which contains a coil into and out of which the specimen is vibrated. Locked-in detection at both the Ac and the vibration frequencies leads to high sensitivity, sufficient to measure the resistivity of a small high-T(c) crystal in the normal state, as well as the real and imaginary parts of the susceptibility in the superconducting state. A simple modification of the circuit, with no disturbance to the specimen, allows the apparatus to be used as a vibrating sample magnetometer.