Magnetic and Critical Properties of Alternating Spin Chain with S=1/2, 1 in Magnetic Fields

Abstract

We study an integrable spin chain with an alternating array of spins S=1/2, 1 in external magnetic fields using the Bethe ansatz exact solution. The calculated magnetization curve has a cusp at a critical magnetic field H=H_C, at which the specific heat shows a divergence property.We also calculate finite-size corrections to the energy spectrum, and obtain the critical exponents of correlation functionsusing conformal field theory (CFT). Low-energy properties of the model are described by two c=1 U(1) CFTs at HC and one c=1 U(1) CFT at H>H_C.