Two-Loop Y-Ba-Cu-O RF-SQUID Magnetometer

Abstract

HT_c RF SQUID magnetometers have been made from Y-Ba-Cu-0 thin films. The small, i. e. 0.3 µm long region of the microbridge was irradiated with 100 keV oxygen ions at an ion dose as low as 1 × 10¹³ 0⁺/cmü. SQUID function was observed up to 86 K. The white noise of the SQUID was 2.5 x 10⁻⁴/${\phi _0}/\sqrt {Hz}$ at 83 K and the 1/f corner frequency was lower than 5 Hz. A SQUID magnetometer with a directly coupled pick-up coil was also made.