Resonant quantum tunnelling and coherence of the Néel vector for different crystal symmetries

Abstract

The phenomena of macroscopic quantum tunnelling and coherence of the Néel vector are investigated for small single-domain antiferromagnetic particles. Both the Wentzel-Kramers-Brillouin exponents and the pre-exponential factors are found exactly for the tunnelling rates, for various forms of the magnetocrystalline anisotropy. The calculations are performed on the basis of the two-sublattice model and the instanton method applied to the spin-coherent-state path integral.