Anomalous spin-lattice relaxation in dilute RhFe at positive and negative nanokelvin temperatures

Abstract

We report investigations at ultra low positive and negative spin temperatures on the spin-lattice relaxation in a rhodium sample with 6 ppm of iron impurities. A strong decrease in the Korringa constant κ, dependent on the inverse of nuclear spin temperature 1/T, was observed in fields below 1 mT; at B=0, the κ was almost two times smaller at T=0.8nK than at -0.8 nK. These results indicate strong modification of magnetic impurity scattering by the large nuclear susceptibility of the host material.