Hysteresis-encoded thermometry in the cryogenic regime using a Dy-single-molecule magnet

Abstract

Precise cryogenic thermometry (<10 K) in single-molecule magnets (SMMs) remains a critical challenge, as conventional approaches often suffer from poor sensitivity and limited applicability. To address this, we present a hysteresis-based thermometry approach with a Dy(III)-SMM, which leverages key magnetic parameters from hysteresis loops to provide a sensitive alternative. Three distinct hysteresis parameters – saturation magnetisation (M_S), remanent magnetisation (M_R), and loop area (A) – have been used in the 2–8 K regime for thermometry. All three parameters decrease monotonically with increasing temperature, and this temperature dependence results in excellent relative thermal sensitivities (S_r), following the trend S^A_r > S^R_r > S^S_r. Furthermore, scan rate-dependent analyses have been performed, showing negligible variations across different sweep rates, confirming the stability of the thermometric response under varying scan conditions. This work represents the first demonstration of hysteresis-based thermometry in SMMs, providing a versatile route for cryogenic sensing by utilising the intrinsic magnetisation dynamics, with promising implications for quantum and low-temperature device applications.