Microscopic investigation of low dimensional magnet Sc₂Cu₂O₅: combined experimental and ab initio approach

Sc₂Cu₂O₅ is a non centro-symmetric oxide comprising of zig-zag chains made up of Cu²⁺ ions in a distorted square planer coordination. We present here a combined experimental and theoretical investigation on this compound, which is based on magnetization, electron spin resonance (ESR), heat capacity as well as density functional theory (DFT) based calculations. Short range magnetic correlation prior to the long range order at K is evidenced by a broad hump like feature (43 K) found in the magnetic contribution of the heat capacity as well as by deviations from a regular Curie–Weiss behavior observed in the bulk magnetization and the Cu²⁺ ESR intensity. The DFT results indicate the existence of ferro-orbital ordering at the Cu-sites, which gives rise to chain like arrangements of Cu ions along the crystallographic b axis. It also signifies complex nature of the spin structure with nonuniform magnetic interactions along the zig-zag chains. The ground state energy is found to be minimum for ferromagnetically coupled spin-dimers along the chains, whereas the adjacent chains are themselves antiferromagnetically coupled. The experimentally observed short range magnetic correlations possibly arise due to this chain like structure. (paper)