Transferred hyperfine field of Rb2CoCl4 single crystals in the ferroelectric–incommensurate–normal phase by 87Rb NMR

The molecular susceptibility and paramagnetic shift of Rb2CoCl4 single crystals grown using the slow evaporation method were measured, and from these experimental results we obtained the transferred hyperfine interaction due to the transfer of spin density from Co2+ ions to Rb+ ions. The transferred hyperfine field was obtained for the ferroelectric, incommensurate, and normal phases. In the case of Rb(I), the transferred hyperfine interaction decreases with increasing temperature in the incommensurate phase, and increases with increasing temperature in the normal phase. The value of Hhf in the incommensurate and normal phases increases abruptly with increasing temperature in the case of Rb(II). These results indicate that the effects due to the transfer of spin density from Co2+ ions to the Rb(I) and Rb(II) ions are large above Ti. In particular, the effect due to the transfer of spin density to Rb(II) ions in the normal phase is very large; the variations with temperature of the transferred hyperfine interactions of the Rb(I) and Rb(II) nuclei are more or less continuous in Tc1 and Ti, and are not affected by the ferroelectric–incommensurate–normal phase transitions.