Electronic structure of spin-shape-1/2 Heisenberg antiferromagnetic systems: Ba2Cu(PO4)(2) and Sr2Cu(PO4)(2)

Abstract

We have employed first principles calculations to study the electronic structure and magnetic properties of the low-dimensional phosphates, Ba2Cu(PO4)(2) and Sr2Cu(PO4)(2). Using the self-consistent tight-binding linearized muffin-tin orbital method and the Nth order muffin-tin orbital method, we have calculated the various intrachain as well as the interchain hopping parameters between the magnetic ions (Cu2+) for both the compounds. We find that the nearest-neighbor intrachain hopping (t) is the dominant interaction suggesting the compounds to be indeed one dimensional. Our analysis of the band dispersion, orbital projected band structures, and the hopping parameters confirms that the Cu2+-Cu2+ super-super exchange interaction takes place along the crystallographic b direction mediated by O-P-O. We have also analyzed in detail the origin of short-range exchange interaction for these systems. Our ab initio estimate of the ratio of the exchange interaction of Sr2Cu(PO4)(2) to that of Ba2Cu(PO4)(2) compares excellently with available experimental results.