ESR Line Shapes and Rotational Modes in the Structurally Incommensurate Phase of {N(CH₃)₄}₂CoCl₄ Crystal

Abstract

ESR line shapes for the tetrahedra SO₄ in β-K₂SO₄ type crystal with symmetry D_2h¹⁶-Pmcn have been calculated as a function of the direction of the applied magnetic field and the rotation of the tetrahedra in the incommensurate phase. The effect of the one-dimensional incommensurate modulation on the line shape depends strongly on the relative orientation between the magnetic field and the rotation axis of the tetrahedra. The analysis has been applied to ESR spectra of Mn ion in {N(CH₃)₄}₂CoCl₄. The result supports the previous conclusion that the rotational axis of the CoCl₄ tetrahedra is parallel to the travelling direction of the modulation wave.