The S=3/2 Heisenberg chain in a magnetic field

Fabian H. L. Eßler, Ian K. Affleck

N Kitanine, Jean Michel Maillet, N. A. Slavnov +1 more

Hiroaki Nakamura, Minoru Takahashi

A nonlinear susceptibilities (the third derivative of a magnetization $m_S$ by a magnetic field $h$ ) of the $S$=1/2 ferromagnetic Heisenberg chain and the classical Heisenberg chain are calculated at low temperatures $T.$ In both chains the nonlinear susceptibilities diverge as $T^{-6}$ and a linear susceptibilities diverge as $T^{-2}.$ The arbitrary spin $S$ Heisenberg ferromagnet $[$ ${\cal H} = \sum_{i=1}^{N} \{ - J{\bf S}_{i} {\bf S}_{i+1} - (h/S) S_{i}^{z} \}$ $(J>0),$ $]$ has a scaling relation between $m_S,$ $h$ and $T:$ $m_S(T,h) = F( S^2 Jh/T^2).$ The scaling function $F(x)$=(2$x$/3)-(44$x^{3}$/135) + O($x^{5}$) is common to all values of spin $S.$

Tetsuji Kuramoto

We study magnetic and critical properties of the alternating spin antiferromagnetic Heisenberg chain with $S=1/2$ and 1 in a magnetic field at T=0. The numerical diagonalization is applied to the system up to $2N=20$ sites. Checking numerically that magnetic states with the magnetization per site $m$ obey a conformal field theory with conformal anomaly $c=1$ for $1/4

Tôru Sakai

Marcio Jose Martins

We discuss some properties of an integrable and conformally invariant Heisenberg chain with alternating spins S and S' (S'>S) in the presence of a magnetic field. The zero-field magnetic susceptibility is computed and turns out to be only dependent on the spin S. For small enough magnetic field, the low-lying excitations are related to the deformed SU(2) parafermionic field theory at levels 2S and 2(S'-S). Generalizations to these results for other mixed systems are commented on.