Novel magnetic sensors using high T_c superconductors

We propose a novel magnetic sensor to apply a new phenomenon in high T _c superconductors of strongly anisotropic materials. We have found periodic oscillations in the flux-flow resistance of Josephson vortices in intrinsic Josephson junctions of single crystalline Bi₂Sr ₂CaCu₂O_g+y fabricated by using a focused ion beam. The periodic oscillations in the flux-flow resistance have been observed at higher magnetic fields than 70 kOe at low temperatures. The period depends only on the junction width perpendicular to the magnetic fields and the current, independent of temperature and magnetic field. The detailed analyses of the oscillations show that the characteristics of the flux-flow device can be applied as magnetic sensors to detect an absolute magnetic field and to measure the field precisely to an accuracy in the 1 mOe range, even under magnetic fields as high as 70 kOe. We believe that this kind of sensor opens up new applications of high T_c superconductors.