Ultrahigh-frequency NMR of Tm 3+ ions in single crystals of thulium ethylsulfate at high magnetic fields

Abstract

Resonant transitions predicted earlier between low-lying electron–nuclear sublevels of the Tm 3+ ground state were observed at frequencies up to 700 MHz in a dielectric Van Vleck paramagnet—thulium ethylsulfate (TmES) single crystal. It is shown that, due to the distortion of the 4f-electron shell of rare-earth ion in an applied magnetic field, the parameters of electron–nuclear interaction become field dependent. Experimental results of second moment of Tm 3+ enhanced NMR line in TmES are presented. The possible mechanisms of line broadening are considered, particularly as a result of the first excited doublet splitting.