Structural Aspects of Magnetic Coupling in CaV4O9

TL;DR

This paper investigates how the layered structure of CaV4O9 influences magnetic interactions, revealing that second neighbor couplings dominate, leading to a complex coupled spin system.

Contribution

It provides a detailed analysis of the exchange interactions in CaV4O9, highlighting the dominance of second neighbor couplings due to structural corrugation.

Findings

Second neighbor couplings are stronger than nearest neighbor.

The V spin occupies a d(x^2-y^2) orbital.

The system consists of two coupled S=1/2 metaplaquette systems.

Abstract

The strong corrugation of the V4O9 layer in the spin gap system CaV4O9 is examined for its impact on the exchange coupling constants between the spin 1/2 V ions. Local spin density (LSD) calculations show that the V spin occupies a d(x^2-y^2) orbital (x and y are the V-V directions). The Kanamori-Goodenough superexchange rules, and the degeneracy of ferromagnetic and antiferromagnetic alignments within LSD, suggest that 2nd neighbor couplings dominate over nearest neighbor, resulting in two coupled S=1/2 metaplaquette systems.