Quantum phase transition in field-induced ordering phases of anisotropic Haldane systems

Abstract Being motivated by the novel phase transition found in the Haldane compound, Ni ( C 5 H 14 N 2 ) 2 N 3 ( PF 6 ) , we have investigated the field-induced quantum phase transitions in the anisotropic S = 1 Haldane system by means of the density matrix renormalization group method. With increasing magnetic fields, in addition to the Haldane to ordered phase transition, the spin-reorientation transition between the ordered phases is predicted to occur in the case where the magnetic field is inclined from the principal axes of the anisotropy. Physical consequences of this transition are discussed in connection with the experimental result.