Available online at www.sciencedirect.com Physica A 320 (2003) 435–442 www.elsevier.com/locate/physa Surface critical behavior of thin Ising lms at the ‘special point’ Najem Moussa a ; ∗ , Smaine Bekhechi b a LMSPCPV, D ept. de Physique, FST, B.P. 509, Boutalamine, Errachidia, Morocco b Department of Physics and Astronomy, University of Manitoba, Winnipeg Canada, R3T 2N2 Received 16 August 2002; received in revised form 18 October 2002 Abstract The critical surface phenomena of a magnetic thin Ising lm is studied using numerical Monte-Carlo method based on Wol cluster algorithm. With varying the surface coupling, js = Js =J , the phase diagram exhibits a special surface coupling jsp at which all the lms have a unique critical temperature Tc for an arbitrary thickness n. In spite of this, the critical exponent of the surface magnetization at the special point is found to increase with n. Moreover, non-universal features as well as dimensionality crossover from two- to three-dimensional behavior are found at this point. c  2002 Elsevier Science B.V. All rights reserved. PACS: 75.10.Hk; 64.60.Fr; 75.70.-i Keywords: Surface critical behavior; Ising lms; Special point 1. Introduction The thin lms of a few atomic layers has attracted much interest [1–4]. However, the interesting results for these systems are the dependence of the critical behavior on the thickness. It was found experimentally, that the Curie temperature and the average magnetic moment per atom increases with the thickness [5,6]. More interesting properties may be expected by taking the eect of the system surfaces. Since the free surface breaks the translational symmetry, much interest has been devoted in order * Corresponding author. E-mail addresses: najemmoussa@hotmail.com (N. Moussa), bekhechi@physics.umanitoba.ca (S. Bekhechi). 0378-4371/03/$-see front matter c  2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0378-4371(02)01738-7