Correlation between Superconductivity and Ferromagnetism in UGe_2(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

概要

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We measured the ac magnetic susceptibility of the ferromagnet UGe_2 that exhibits superconductivity at high pressures within a ferromagnetic phase. It is known that the ferromagnetic phase is separated into two phases and thus there are two critical pressures, namely, P_X∿12kbar at which an unknown phase transition terminates and P_<FM>∿16kbar at which a Curie temperature is suppressed to zero. We observed the following features in the vicinity of P_X : the discontinuity in the plot of superconducting transition temperature versus pressure, the maximum superconducting volume fraction in contrast to the small volume fraction near P_<FM>, and the markedly enhanced initial slope of the upper critical magnetic field (exceeding 200kOe/K). These results indicate that the superconductivity directly correlates with P_X. We conclude therefore that it is the critical point P_X, rather than P_<FM>, that plays a crucial role in the appearance of the superconductivity.
社団法人日本物理学会の論文
2005-03-15