Anisotropic spin fluctuations in the triangular Kondo lattice compound CePtAlGe probed by site-selective Al NMR

Sakai, Hironori   ; Shin, S.*; Kambe, Shinsaku  ; Tokunaga, Yo  ; Harima, Hisatomo*; Pomjakushina, E.*; Park, T.*

We report site-selective Al nuclear magnetic resonance (NMR) measurements on the Kondo-lattice compound CePtAlGe, in which Ce ions form triangular layers. By combining the measured nuclear quadrupole parameters with calculated electric field gradients, we unambiguously assign the two inequivalent Al sites and determine distinct hyperfine coupling constants dominated by Ruderman-Kittel-Kasuya-Yosida (RKKY)-type transferred fields. Spin-lattice relaxation reveals pronounced anisotropic spin fluctuations, and comparison of the two sites constrains their momentum-space structure. At low magnetic fields, is strongly enhanced on cooling toward the Nel temperature, evidencing the growth of in-plane antiferromagnetic correlations in the paramagnetic state.