Pseudo Temperature Independent Paramagnetism in Co₂Si₅N₈ Nitridosilicate

Herein, the synthesis of Co2Si5N8 nitridosilicate from alpha-Ca2Si5N8 by ion exchange is described. The monoclinic Co2Si5N8 structure (space group Cc) is compared with those of the related nitridosilicates Ca2Si5N8 and Fe2Si5N8 its magnetic properties are profoundly investigated. Most interestingly, polycrystalline Co2Si5N8 exhibits a quasi-temperature-independent paramagnetic susceptibility of about 6x10(-3) cm(3) mol(-1) over a wide temperature range from 100 to 600 K. Two different magnetic models based on a phenomenological Hamiltonian that takes into account magnetic exchange coupling, crystal-field interactions, and Zeeman effects within the framework of an angular momentum basis set are refined to the experimental susceptibility datasets. The results of the refinements point to the realization of a pseudo temperature independent paramagnetism for Co2Si5N8 that results from a near-perfect cancellation of temperature-dependent contributions to the susceptibility depending delicately on the mixing of ion levels in the electronic states, their relative energies, and the magnetic coupling between them. Additionally, performed direct current field scan, alternating current susceptibility, and heat capacity measurements complete the magnetic characterization and facilitate the identification of impurity phase contributions.