Low-temperature NMR studies of SrB6

We report the results of a B-11 nuclear magnetic resonance (NMR study Of Sr B6 at temperatures between 0.1 and 30 K and in a magnetic field of 4.74 T. Below 30 K the NMR spectrum is temperature independent but the spin-lattice relaxation rate T-1(-1) exhibits different features in two different tempe rature regimes. At high temperatures, between 30 K and a field-dependent cr ossover temperature T-B between 0.5 and 2 K.T-1(-1) is almost temperature i ndependent. We point out that for T in the crossover temperature range the magnitude of T-1(-1) of SrB6 is distinctly larger than for LaB6, a metal wi th a charge carrier concentration at least two orders of magnitude higher t han that of SrB6. A possible cause for this behavior maybe the very weak it inerant Ferromagnetism that has subsequently been established to occur in n ominally pure SrB6. At low temperatures. below T-b, T-1(-1) decreases subst antially with decreasing temperature confirming a cross-over or phase trans ition phenomenon as observed by measurements of thermal and transport prope rties. (C) 2000 Elsevier Science B.V. All rights reserved.