Magnetic properties of S=1 spin chains with alternating interactions

Abstract Magnetic properties of S =1 antiferromagnetic spin chains with alternating nearest-neighbor and competing next-nearest-neighbor interactions are studied, using the strong coupling expansion as well as numerical methods. Characteristic features of this system such as magnetization plateau, field-induced long-range ordering and incommensurate behavior are discussed in connection with the dimer gap, focusing on a novel role of the anisotropy.