Thermodynamic and Magnetic Properties of the System Ca₃Co_2-<i>x</i>Zn<i>_x</i>O₆

The crystal structure of Ca₃Co₂O₆ is built from chains of Co³⁺ ions that are separated by Ca ions. Magnetic moments associated with low-spin Co ions are located on trigonal prismatic sites within the spin chains. Ferromagnetic intrachain interactions are an order of magnitude stronger than antiferromagnetic interchain interactions, leading to a quasi-one-dimensional magnetic structure. In an effort to study its magnetic state, we substituted Zn²⁺ for Co³⁺ ions. Zinc ions occupy the trigonal prismatic (magnetic) sites and charge balance causes low spin Co³⁺ ions occupying octrahedral sites to become low-spin Co⁴⁺. Thus, Zn substitution dilutes moments on trigonal prismatic sites and induces them on octahedral sites. Samples of Ca₃Co_2-xZn_xO₆ were synthesized via solid state reaction and phase purity was evaluated via x-ray diffraction. X-ray diffraction elucidated a solubility limit near x = 0.1. Heat capacity and magnetization were measured as a function of temperature and were used to construct a T vs. x phase diagram for Ca₃Co_2-xZn_xO₆. In this poster, this phase diagram will be compared to the previously reported phase diagrams for Ca₃Co_2-xR_xO₆ with R = Cu, Cr, Fe, Mn, Sc, and Ho.