Magnetic order in the two-dimensional compass-Heisenberg model
1 Joint Institute for Nuclear Research,
2 Institut für Theoretische Physik, Universität Leipzig, 04109 Leipzig, Germany
Received in final form: 28 April 2015
Published online: 8 June 2015
A Green-function theory for the dynamic spin susceptibility in the square-lattice spin-1/2 antiferromagnetic compass-Heisenberg model employing a generalized mean-field approximation is presented. The theory describes magnetic long-range order (LRO) and short-range order (SRO) at arbitrary temperatures. The magnetization, Néel temperature TN, specific heat, and uniform static spin susceptibility χ are calculated self-consistently. As the main result, we obtain LRO at finite temperatures in two dimensions, where the dependence of TN on the compass-model interaction is studied. We find that TN is close to the experimental value for Ba2IrO4. The effects of SRO are discussed in relation to the temperature dependence of χ.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2015