Bond-operator analysis of the magnetization of spin chains

A bond operator representation of quantum S = 1 spins is developed along th e same line to the bond operator representation of quantum S = 1/2 spins. T he 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 effecti ve Hamiltonians of the S = 1/2 pseudospins in the effective external magnet ic 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 rig orous results of the spin-1/2 XXZ spin chains. For spin-1 chains, the depen dences of the magnetization on the applied magnetic fields are obtained. Th e m = 1/4 plateau appearing in the magnetization of the spin-1/2 spin ladde rs 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 th e related experiments on spin-1 spin ladders are discussed also.