Abstract:
A sharp jump in the magnetic response near the first critical twins magnetic field $H_{ic1}$ was generated under the combined action of a constant biased and a local oscillating damped magnetic fields on the surface of the YBa$_2$Cu$_3$O$_{7-x}$ epitaxial film. The possibility of increasing due to this jump the sensitivity of a standard Hall magnetometer from $\sim$ 2.5 $\cdot$ 10$^{-3}$ Gs/Hz$^{1/2}$ to $\sim$ 8 $\cdot$ 10$^{-7}$ Gs/Hz$^{1/2}$ in the frequency range $\sim$ 1 kHz has been demonstrated. The range of the measured magnetic fields of the magnetometer was extended to the region of weak fields $\sim$ (8 $\cdot$ 10$^{-7}$–2.5 $\cdot$ 10$^{-3}$) Oe, while maintaining the accuracy and linearity of the order of $\sim$ 0.01%. To increase the sensitivity, linearity and noise sustainability the beginning of the operating point of the magnetometer was shifted to the twins values $H_{ic1}$. The increased spatial resolution of the magnetometer, determined by the linear dimensions of the YBa$_2$Cu$_3$O$_{7-x}$ film twins, was provided by an increase in the total magnetic field directed perpendicular to the film surfaces and the Hall transducer and reached $\sim$ 300 nm.
Keywords:the twin high temperature superconductor, the density jump of the trapped magnetic flux, biased magnetic field, oscillating damped local magnetic bias field, two-stage Hall magnetometer.