Bond-operator analysis of the magnetization of spin chains

A bond operator representation of quantum S = 1 spins is developed along the same line to the bond operator representation of quantum S = 1/2 spins. The two representations are then applied to investigate the magnetization of the isotropic spin-1 antiferromagnetic chains and the spin-1/2 and spin-1 spin ladders. With the appropriate quantum states projected our, the spin-1 chains and the spin-1/2 and spin-1/2 spin ladders can be mapped to effective Hamiltonians of the S = 1/2 pseudospins in the effective external magnetic fields. The magnetization features of the spin-1 chains and the spin-1/2 and spin-1 spin ladders are then analyzed with the use of the existing rigorous results of the spin-1/2 XXZ spin chains. For spin-1 chains, the dependences of the magnetization on the applied magnetic fields are obtained. The m = 1/4 plateau appearing in the magnetization of the spin-1/2 spin ladders and the m = 1/4, 1/2, and 3/4 plateaus in the magnetization of the spin-1 spin ladders are studied. The effects of the single-ion anisotropy and the related experiments on spin-1 spin ladders are discussed also.