Spin solitons and spin waves in chiral and racemic molecular based ferrimagnets

Abstract

Resonant modes corresponding to a spin-soliton resonance (SSR) and a spin-wave resonance (SWR) have been detected and distinguished in the spectra of the electron spin resonance (ESR) of two-dimensional $[\text{Cr}{(\text{CN})}_{6}][\text{Mn}(\text{S})\text{\ensuremath{-}}pn\text{H-}({\text{H}}_{2}\text{O})]{\text{H}}_{2}\text{O}$ [green needle (GN)] chiral single crystals and three-dimensional ${[\text{Mn}{(\text{R}/\text{S})\text{\ensuremath{-}}pn}]}_{2}$ $[\text{Mn}{{(\text{R}/\text{S})\text{\ensuremath{-}}pn}}_{2}({\text{H}}_{2}\text{O})]{[\text{Cr}{(\text{CN})}_{6}]}_{2}$ [yellow needle (YN)] single crystals. The spin-soliton resonance has been detected in the ESR spectrum of the chiral YN crystals and has not been observed in the spectra of the racemic GN crystals. This is a direct experimental evidence that the collective spin excitations in molecular magnetic crystals depend on the crystal chirality. The temperature and the angular dependences of the effective exchange constants obtained from the ESR spectra are in good agreement with the experimental data received by means of a superconducting quantum interference device magnetometry. The temperature dependencies of the magnetic susceptibilities corresponding to the integral intensities of the resonance lines are different for the SSR and the SWR contributions to the ESR spectrum. It enables us to distinguish the nature of the resonant lines in the intermixture of two sequences of the resonance lines, which have been measured for arbitrary orientations of the static external magnetic field.