Anomalous NMR spin-lattice relaxation in SrB6 and Ca1-xLaxB6 - art. no. 140410

We report the results of B-11 nuclear magnetic resonance (NMR) measurements of SrB6 and Ca(0.995)Lao(0.005)B(6) below room temperature. Although the e lectrical resistivities of these two materials differ substantially, their B-11-NMR responses exhibit some strikingly common features. Both materials exhibit ferromagnetic order, but their B-11-NMR spectra reveal very small h yperfine fields at the boron sites. The spin-lattice relaxation T-1(-1) var ies considerably with external field but changes with temperature only belo w a few K. We discuss these unusual results by considering various differen t scenarios for the electronic structure of these materials.