Uniaxial and vortex-state magnetic tunnel junction sensors for cryogenic quantum applications

Magnetic tunnel junctions (MTJs) have emerged as key technologies in cryogenic sensing platforms for quantum metrology and superconducting circuits. We present a systematic temperature-dependent comparison of uniaxial and vortex-state MTJ sensors from 10-300 K, highlighting how device geometry and magnetization reversal dynamics govern low-field performance. Both sensor types exhibit enhanced tunnel magnetoresistance (TMR) upon cooling, yet the vortex-state maintains a constant sensitivity, with a temperature coefficient of -105 ppm/K, while the uniaxial design loses 17% sensitivity due to increased magnetic hysteresis. These results establish that low-temperature TMR enhancement alone does not guarantee sensor performance. We demonstrate that vortex-state MTJs exhibit robust, thermally stable detection suitable for quantum devices requiring reliable magnetic-field readout across cryogenic temperatures.