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73Ge-NMR/NQR Investigation of Magnetic Properties of URhGe

We report 73Ge-NMR and NQR results for ferromagnetic (FM) superconductor URhGe. The magnitude and direction of the internal field, H_int, and parameters of the electric field gradient at the Ge site were determined experimentally. Using powdered polycrystalline samples oriented by different methods, the field dependences of NMR shift and nuclear spin relaxation rates for H_0 // c (easy axis) and H_0 // b were obtained. From the NMR shifts for H_0 // b, we confirmed a gradual suppression of the Curie temperature and observed a phase separation near the spin reorientation. The observation of the phase separation gives microscopic evidence that the spin reorientation under H_0 // b is of first order at low temperatures. The nuclear spin-lattice relaxation rate 1/T_1 indicates that the magnetic fluctuations are suppressed for H_0 // c, whereas the fluctuations remain strongly for H_0 // b. The enhancements of both 1/T_1T and the nuclear spin-spin relaxation rate 1/T_2 for H_0 // b toward the spin reorientation field suggest that the field-induced superconductivity in URhGe emerges under the magnetic fluctuations along the b axis and the c axis.