NMR investigation of crystalline electric field effect on spin-spin relaxation in (Y(1-x)RE(x))Rh4B4

Pulsed and CW-NMR measurements of sup 11 B have been used to study the spin dynamics of magnetic rare earth ions in (Y sub (1-x) RE sub x)Rh4B4. Findings indicate that the nuclear spin-lattice relaxation rate of sup 11 B induced by RE = Tb, Dy and Ho moments is exponential in - DELTA T in the normal state, where DELTA is the crystal field splitting of the first excited state. Anomalous temperature dependencies of the transverse relaxation time T2, Knight shift and NMR line width in (Y sub(1-x)Dy sub x) Rh4B4 are obtained in the temperature region where T1 changes drastically. The results are discussed. in terms of a model of the crystalline electric fields, in which thermal activation across (DELTA) must take place for the DELTA m sub J = + or - 1 transition to occur in highly anisotropic paramagnetic moments in the ternary superconductors.