Spin-chain magnetism in Eu-dopedCa3Co2O6andCa3CoRhO6investigated by Mössbauer spectroscopy

Abstract

We report the results of $^{151}\text{E}\text{u}$ M\"ossbauer effect and magnetization measurements in the Eu-doped ${\text{Ca}}_{3}{\text{Co}}_{2}{\text{O}}_{6}$ and ${\text{Ca}}_{3}{\text{CoRhO}}_{6}$, which are of great current interest in the fields of spin-chain magnetism and geometrical frustration. We find that there is a pronounced increase in the linewidth of the M\"ossbauer spectra below a certain temperature $({T}^{\ensuremath{\ast}})$ that is well above the one at which three-dimensional magnetic ordering features set in. This unusual broadening of the spectra indicates the existence of a characteristic temperature in these ``exotic'' magnetic systems, which is attributable to the onset of incipient one-dimensional magnetic order. This is inferred from an intriguing correlation of ${T}^{\ensuremath{\ast}}$ with the paramagnetic Curie temperature (a measure of intrachain coupling strength in these cases).