Field-angular dependence of pairing interaction in URhGe; Comparison with UCoGe

Tokunaga, Yo  ; Aoki, Dai*; Mayaffre, H.*; Krmer, S.*; Julien, M.-H.*; Berthier, C.*; Horvati, M.*; Sakai, Hironori   ; Kambe, Shinsaku  ; Hattori, Taisuke; Araki, Shingo*

The field-angular dependence of Co-NMR spin-lattice relaxation rate has been measured for a 10% Co-doped single crystal of URhGe. The experiment revealed that spin fluctuations in ferromagnetic (FM) state of URhGe are robust against magnetic field below about 4 T, applied along any direction in the crystal plane. This is in clear contrast with the sister compound UCoGe, in which FM spin fluctuations are rapidly suppressed by a tiny applied field along the axis. We show that such a difference in the character of the spin fluctuations is reflected in their two distinct phase diagrams for the upper critical field , providing further support to the mechanism of superconductivity mediated by spin fluctuations in these materials.