Finite-size-scaling study of the anisotropic spin-1/2 Ashkin-Teller model

Using transfer-matrix finite-size-scaling (TMFSS), we investigate the aniso tropic spin-1/2 Ashkin-Teller model (ATM) where the two bilinear interactio ns are different (L-2 not equal J(2)) and with a four coupling interaction K-4. Conclusive numerical evidence is obtained, indicating the presence of another partially ordered phase in the phase diagram. Also, from exponents calculations we show that all the transitions are in the Ising universality except for the multicritical point B-4 which is nonuniversal. (C) 2000 Els evier Science B.V. All rights reserved.