Large self-heating by trapped-flux reduction in Sn-Pb solders

Magnetic flux trapping in field-cooled (FC) Sn-Pb solders has been recently studied because of the observation of nonvolatile magneto-thermal switching ( Arima H. et al ., Commun. Mater. , 5 (2024) 34) and anomalous magnetic field-temperature ( H - T ) phase diagrams ( Murakami T. et al ., AIP Adv. , 13 (2023) 125008). In this paper, we investigate the origin of the anomalously low specific heat ( C ) in Sn10-Pb90 and Sn45-Pb55 solders after FC at H = 1500 Oe. We show that the FC solders exhibit self-heating possibly caused by the flux flow during the reduction of trapped fluxes when heating the sample during the C measurements. The T dependence of T rise clearly exhibits unexpectedly large values when the low- C states are observed. In addition, the cause of the transition-like behavior in C - T of FC solders is explained by local heating during H control and flux-jump phenomena.