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

\n\nMagnetic flux trapping in field-cooled (FC) Sn-Pb solders has been recently studied because of the observation of nonvolatile magneto-thermal switching (<sc>Arima</sc> H. et al., Commun. Mater., 5 (2024) 34) and anomalous magnetic field-temperature (H-T) phase diagrams (<sc>Murakami</sc> 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.\n