Low-temperature Mössbauer spectroscopy: Evaluation of cation distribution in CoFe2O4

Abstract

We hereby present methodological study of Mössbauer spectroscopy used to determine the site distribution of cations in well-crystallized CoFe2O4 powders with an average size of 100 nm. Understanding the distribution of Co and Fe in octahedral and tetrahedral sites of spinel lattice is of crucial importance in defining magnetic properties of cobalt ferrite nanopowders. The purpose of this report is to find both the optimal experimental conditions and the most reliable fitting model (as simple as possible) for estimating the actual cation distribution. Various fitting models were tested for measurements carried out over a wide range of temperatures and an applied magnetic field. Moreover, we show that the Mössbauer spectrum at room temperature is not suitable for reliably estimating the cation distribution, meaning that measurements at low temperatures are necessary. Given that zero field measurements carried out at 80 K provide the same quantitative information as zero field and in-field measurements at 5 K, we argue that in-field measurements as well as liquid He are not required to obtain reliable fit results. The conclusions of Mössbauer method are consistent with the results obtained by vibrating sample magnetometry and X-ray absorption spectroscopy at the l-edges of Fe and Co.