Magnetic state dynamics in itinerant paramagnet UM3B2 (M = Co, Ir) probed by 11 B NMR

Abstract We have carried out the 11 B NMR measurement on the itinerant paramagnetic systems UM 3 B 2 (M = Co, Ir) to investigate the low-dimensional characteristics of the 5f-electrons due to thestructural anisotropy. The recent X-ray analysis suggests that UIr 3 B 2 has a different structuremodulated from the ever-known superlattice. The azimuth angle variation of NMR spectrumwithin the ab-plane clarified that B atoms occupy the single site, and a certain ligands arrangementsurrounding B atom turns to the same orientation as the another one through the three- or six-fold rotation around the c-axis. These results have been consistent with the X-ray proposition. Toevaluate the temperature (T) development of general susceptibility (χ q,ω ), Knight shift and nuclearspin-lattice relaxation rates measurements were performed and the similar variations of χ q,ω wereidentified in both UCo 3 B 2 and UIr 3 B 2 . Above a crossover point defined as T ∗ ≃ 50 K, the evolutionof χ q,ω is dominant at q = 0, suggesting that ferromagnetic correlations develop in high-T regimes;meanwhile, below T