Cryogenic Magnetic Field Sensors and Magnetic Field-Controlled Supercurrent Switches Based on Ferromagnetic/Superconducting/Ferromagnetic Trilayers: the Performance of NiFe/Nb/NiFe and Co/Nb/Co

Abstract

In the last decades, many superconductor-based devices have been utilized in practical applications that refer to the production/sensing of ultra-high/low magnetic fields, resistive storage of data, etc. The superconducting magnetoresistance effect (sMRE) observed in ferromagnetic/superconducting/ferromagnetic trilayers (TLs) has been widely studied in the literature. Here, we investigate Ni80Fe20/Nb/Ni80Fe20 and Co/Nb/Co TLs on a comparative basis and we provide technical guidelines that empower us to design magnetic field sensors and magnetic field-controlled supercurrent switches for cryogenic applications. The performance of these TLs has been studied in great detail. It turned out that Ni80Fe20-based TLs are applicable in the regime of low magnetic fields (on the order of a few hundred Oe) due to their magnetically soft character, while Co-based ones are effective at relatively higher magnetic fields (on the order of a few thousand Oe) owing to their magnetically harder behavior. The Ni80Fe20-based TLs exhibit a sMRE magnitude, (Rmax − Rmin)/ Rnor ×100 %, on the order of 30–50 % and a field sensitivity, d R(H)/dH, on the order of 4.0–6.0 mOhm/Oe. The Co-based TLs have higher sMRE magnitude on the order of 30–100 %; however, they exhibit lower field sensitivity on the order of 0.3–0.6 mOhm/Oe. Finally, the Co-based TLs exhibit an abnormal behavior of the upper critical field line, Hc2(T), at low magnetic fields. This feature is absent in the Ni80Fe20-based TLs. Due to the differences outlined above, the Ni80Fe20-based and Co-based TLs can be possibly utilized in two distinct categories of devices, namely magnetic field sensors and magnetic field-controlled supercurrent switches, respectively.