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 [H. Arima et al., Commun. Mater. 5, 34 (2024)] and anomalous magnetic field-temperature (H-T) phase diagrams [T. Murakami et al., AIP Adv. 13, 125008 (2023)]. 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 are explained by local heating during H control and flux-jump phenomena.