P. Santini et al., QUANTUM FLUCTUATIONS AND ANISOTROPY IN QUASI-ONE-DIMENSIONAL ANTIFERROMAGNETS, Physical review. B, Condensed matter, 56(9), 1997, pp. 5373-5379
In the quasi-one-dimensional antiferromagnets CsMnBr3 and RbMnBr3 the
magnetization produced by an external magnetic field displays a much s
tronger dependence upon the direction of the field than expected from
calculations done for a system of classical spins at zero temperature.
By performing these calculations for a system at the temperature at w
hich experiments were made it has been shown that thermal fluctuations
may account for the observed anisotropy of the magnetization. We anal
yze here the role of quantum fluctuations. We find that the spin-wave
approximation does not give meaningful results when applied to these s
ystems and explain why this is so. We perform then density-matrix reno
rmalization-group calculations, which show that the anisotropy is enha
nced over its classical value by quantum fluctuations already at T=0.