Journal of the Physical Society of Japan
Transverse Antiferromagnetism of a Magnetized Haldane-Gap System
Tôru Sakai, Minoru Takahashi
Abstract
A 1D S =1 Heisenberg antiferromagnet in a magnetic field H (// z -axis) at T =0 is studied by numerical diagonalizations. It is found that a phase transition exists at H c1 (=Δ), where Δ is the Haldane gap, and the transverse staggered susceptibility χ st x x diverges and the spin correlation is asymptotically < S 0 x S r x >∼(-1) r r -η between H c1 and H c2 (=4). If the system is quasi-1D, even small interchain interactions can make canting Néel order within a mean field approximation for interchain interactions. This is consistent with a recent NMR measurement for NENP at low temperature.