Hysteresis-Encoded Thermometry in the Cryogenic Regime Using 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 r A > S r R > S r S . Further scan rate-dependent analyses were 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 simple and versatile route for cryogenic sensing by utilising the intrinsic magnetisation dynamics, with promising implications for quantum and low-temperature device applications.