A ug 1 99 8 Quantum Coherence Oscillations in Antiferromagnetic Chains

Macroscopic quantum coherence oscillations in mesoscopic antiferromagnets appear when the anisotropy potential creates a barrier between the antifer-romagnetic states with opposite orientations of the Neel vector. This phenomenon is studied for the physical situation of the nuclear spin system of eight Xe atoms arranged on a magnetic surface along a chain. The oscillation period is calculated as a function of the chain constant. The environmental decoherence effects at finite temperature are accounted assuming a dipole coupling between the spin chain and the fluctuating magnetic field of the surface. The numerical calculations indicate that the oscillations are damped by a rate ∼ (N − 1)/τ , where N is the number of spins and τ is the relaxation time of a single spin.