Fabrication and Characteristics of High-T-c Superconducting/Magnetoresistive Mixed Sensors
Journal
IEEE Transactions on Applied Superconductivity
Journal Volume
26
Journal Issue
3
Pages
1800704
Date Issued
2016
Author(s)
Abstract
Bicrystal grain boundary La0.7Ca0.3MnO3 (LCMO) tunneling magnetoresistance (TMR) mixed sensors with high-Tc superconducting YBa2Cu3Oy (YBCO) transformers have been designed and fabricated. The mixed sensors show an increase in low-field magnetoresistance (MR) ratios at low temperatures and an increase in the slope of low-field MR curve at temperatures below superconducting critical temperature Tc, indicating that the flux related to the field indeed can be captured by the superconducting YBCO loop with a constriction associated to the LCMO TMR junctions. Furthermore, the spin polarization parameter P of 0.40 for LCMO at 10 K is obtained, and the temperature-dependent P can be fitted by the curves of P(T)α(TC-T)0.97±0.01 with TC=296K. The temperature dependence of surface magnetization MS(T) deduced from P(T) agrees with the theoretical models for MS(T) and leads to the conclusion that the charge carriers at the grain-interface boundary govern the tunneling conductivity for our bicrystal grain boundary junctions. In addition, the gain of mixed sensor as a function of temperature gets weaker as T approaching Tc. According to the voltage noise level of 6.8 μV/Hz1/2 and the low-field slope of resistance variation dR/dH 781 κΩ/T for the mixed sensor at 77 K, we obtain the field sensitivity SH1/2 of ∼0.58 μT/Hz1/2.
Type
journal article