Spin-Peierls State vs Antiferromagnetic State. III. Effects of Magnetic Field

Abstract

The phase diagram of the stable states in the presence of the magnetic field is obtained for the quasi-one-dimensional Heisenberg antiferromagnet coupled with the lattice distortion. The spin-flop state and the state having spin-solitons appear as the possible ground states besides the spin-Peierls state and the Néel state which are the ground state in the absence of the magnetic field. Three types of field-induced phase transitions are shown to exist depending on the relative strength of the weak interchain exchange interaction to the spin-lattice coupling.