Spin fluctuations of the uranium 5f-electrons in UN according to 14N-NMR data

Abstract

The results of the study of the paramagnetic region of uranium mononitride by the method of nuclear magnetic resonance (NMR)of 14N nuclei are presented.The 14N NMR spectra, the Knight shifts K, the spin-lattice relaxation times T1 have been obtained within the temperature range T = 60 – 375 K and at magnetic fields 92.8 kOe and 117.5 kOe. The temperature dependence of the Knight shift of the 14N line is proportional to the spin susceptibility χ of 5f-electrons of uranium. The ratio of the experimentally determined value TT1K2 to the theoretically calculated value of the Korringa contribution is 21.5 (at T = 295 K), which is significantly more than for common metals. This suggests that nuclear relaxation is based on the same mechanism as the Knight shift, namely, the indirect connection between the 14N nuclei and the localized magnetic moments of uranium through conduction electrons. The experimental results on the T-dependence of the spin-lattice relaxation rate of 14N also do not contradict the assumption that uranium mononitride is a concentrated Kondo system.