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.
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Received: 24 July 1997 / Accepted: 30 September 1997
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Lü, R., Zhu, JL., Chen, X. et al. Macroscopic quantum coherence of the Neel vector in antiferromagnetic system without Kramers' degeneracy. Eur. Phys. J. B 3, 35–40 (1998). https://doi.org/10.1007/s100510050281
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DOI: https://doi.org/10.1007/s100510050281