Quantum coherence in small antiferromagnets

An antiferromagnetic particle with an excess spin (j) over right arrow has 2 degrees of freedom. The one associated with (j) over right arrow is ferromagnetic, while the antiferromagnetic behavior involves Neel vector (n) over right arrow. It is shown that the spin-parity effect described by Loss et al. has to do with the ferromagnetic degree of freedom and does nor imply the localization of (n) over right arrow for small enough particles for half-integer spin. It is also shown that the tunnel splitting associated with (n) over right arrow is insensitive to applied fields.