Theoretical study of anisotropic layered antiferromagnets

TL;DR

This paper develops a field theory for layered antiferromagnets on BCT lattices, revealing that inter-layer interactions are driven by thermal fluctuations and demonstrating a 2D-3D crossover in magnetic order.

Contribution

It introduces a theoretical framework connecting lattice Heisenberg models to continuum field theories for layered antiferromagnets, highlighting the role of thermal fluctuations in inter-layer interactions.

Findings

Inter-layer interactions are purely thermal fluctuation effects.

Ground state exhibits perfect in-layer antiferromagnetic order.

Demonstrates 2D-3D dimensional crossover in antiferromagnets.

Abstract

We develop the field theory of antiferromagnets to layered structures on BCT crystal lattices with nearest-neibour and next-nearest-neighbour ferro- and/or antiferromagnetic interactions. For this aim the field theoretical counterpart of a lattice Heisenberg model is derived by standard theoretical methods: Hubbard-Stratonovich transformation and a generalized mean-field approach. We shown that the inter-layer interactions are a pure thermal fluctuation effect whereas the ground state is characterized by a perfect in-layer antiferromagnetic order and a lack of inter-layer coupling. This is a demonstration of 2D-3D dimensional crossover which is supposed to occur in real antiferromagnets, for example, in the spin-dimer antiferromagnet BaCuSi2O6.