Evidence for Uniform Coexistence of Ferromagnetism and Unconventional Superconductivity in UGe_2 : A ^<73>Ge-NQR Study under Pressure(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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We report on the itinerant ferromagnetic superconductor UGe_2 through ^<73>Ge-NQR measurements under pressure (P). The P dependence of the NQR spectrum signals a first-order transition from the low-temperature (T) and low-P ferromagnetic phase (FM2) to high-T and high-P one (FM1) around a critical pressure of P_x∿1.2GPa. The superconductivity exhibiting a maximum value of T_<sc>=0.7K at P_x∿1.2GPa, was found to take place in connection with the P-induced first-order transition. The nuclear spin-lattice relaxation rate 1/T_1 has probed the ferromagnetic transition, exhibiting a peak at the Curie temperature as well as a decrease without the coherence peak below T_<sc>. These results reveal the uniformly coexistent phase of ferromagnetism and unconventional superconductivity with a line-node gap. We remark on an intimate interplay between the onset of superconductivity and the underlying electronic state for the ferromagnetic phases.
社団法人日本物理学会の論文
2005-02-15