Eur. Phys. J. B 3, 35-40 (1998)
https://doi.org/10.1007/s100510050281

Macroscopic quantum coherence of the Neel vector in antiferromagnetic system without Kramers' degeneracy

Department of Physics, Tsinghua University, Beijing, 100084, P.R. China

Corresponding author: ^a rlu@Phys.Tsinghua.edu.cn

Received: 24 July 1997
Accepted: 30 September 1997
Published online: 15 May 1998

Abstract

At low temperatures the Neel vector in a small antiferromagnetic particle can possess quantum coherence between the classically degenerate minima. In some cases, the topological term in the magnetic action can lead to destructive interference between the symmetry-related trajectories for the half-integer excess spin antiferromagnetic particle. By studying a macroscopic quantum coherence problem of the Neel vector with biaxial crystal symmetry and a weak magnetic field applied along the hard axis, we find that the quenching of tunnel splitting could take place in the system without Kramers' degeneracy. Both the Wentzel-Kramers-Brillouin exponent and the pre-exponential factors are found exactly for the tunnel splitting. Results show that the tunnel splitting oscillates with the weak applied magnetic field for both the integer and half-integer excess spin antiferromagnetic particles, and vanishes at certain values of the field. All the calculations are performed based on the two sublattices model and the instanton method in spin-coherent-state path integral.