Abstract
ESR spectra of Mn2+ doped in the {N(CH3)4}2CoCl4 crystal were observed in the normal, incommensurate and commensurate phases. The D tensor in the normal phase was determined from the angular dependence of the spectrum. It was concluded from the symmetry of the D tensor that Mn2+ ions were replaced at Co sites. Splitting and broadening of the lines were observed even in the incommensurate phase. The lines which corresponded to the commensurate structure were observed near the incommensurate-commensurate transition temperature in the incommensurate phase.