Spin Relaxation of the F_A(Li) Center in KCl Due to the Hyperfine Interaction Modulated by the Tunneling Li⁺ Ion —Electric Field Effects on the Spin Relaxation—

Abstract

The spin relaxation of the F_A(Li) center in KCl has been explained by proposing a mechanism due to the hyperfine interaction modulated by the tunneling Li⁺ ion. The electric field effects on the relaxation times, which were measured using microwave saturation and saturation recovery methods of ESR, were analyzed using theoretically derived formulae. From the analysis, the tunneling parameters of level splitting Δ=0.2 meV, dipole moment p=1.4 eA, a quantity α=0.5, which could measure overlapping of tunneling wavefunctions, the rms value of fluctuating magnetic fields (=3.1 Oe) and correlation time (=1.7×10⁻⁸ sec) were determined. From theoretical comparison of the observed isotope ratio of the spin lattice relaxation time, the isotope ratio, that α(⁶Li)=1.2α(⁷Li), was derived when the ratio, that Δ(⁶Li)=1.4Δ(⁷Li), was adopted.