The magnetization process of an Ising-type frustrated S=1 spin chain

The magnetization process of an Ising-type S = 1 spin chain with nearest-neighbour interaction (J(1)), next-nearest-neighbour interaction (J(2)) and single-ion anisotropy (D) is investigated on the basis of the ground state phase diagram of the chain in a magnetic field (H greater than or equal to 0). The 49 possible spin structures for the ground state are obtained using Morita's theorem. The magnetization process is obtained from the ground state phase diagram, giving J(2)/J(1) versus H/J(1), determined by comparing the energies of the 49 spin structures. It is shown that (1) among the 49 spin structures, 14 structures with unit cells of <+>, <0>, <+->, <+0>, <+ + ->, <+ + 0>, <+ - 0>, <+00>, <+ + - ->, <+ + 0->, <+ + 00>, <+ + -0>, <+ - +00> and <+ + -0 + 0-> appear in the phase diagram; (2) the magnetization process is equivalent to that of the usual Ising model for D less than or equal to 0; (3) a long period spin structure, <+ + -0 + 0->, is realized for the intermediate ranges of J(2)/J(1) and D/J(1) due to the frustration of the system.