DC and AC magneto-resistance measurement technique for YBa2Cu3O7-δ thin films in megagauss fields

We have developed a technique for measuring DC and AC magnetoresistance in very high magnetic fields in the megagauss range. We performed four terminal DC transport measurements in megagauss fields by minimizing the sample size and the area of the measurement circuit perpendicular to the magnetic field. The use of a high frequency digital lock-in technique was found to improve the signal to noise ratio. Using this technique, we measured the DC and AC magnetoresistance of YBa2Cu3O7-δ thin films at temperatures between 4.2 and 100 K in magnetic fields parallel to the c-axis in magnetic fields up to 130 T. (orig.)