Anomaly of Magnetization in the Superconducting Mixed State of UPt_3

抄録

Magnetization curves of UPt₃ along the c-axis were measured at low temperatures down to 80, mK. Below 350, mK a peak of the irreversible magnetization was found just below the superconducting upper critical field H_c2. However, the peak disappeared above 390, mK, which is much lower than the superconducting critical temperature of 580, mK, suggesting an unconventional mechanism of the flux pinning near H_c2. No distinct anomaly was observed in the magnetization curves at the phase transition between B and C superconducting phases.