Trimodal random-field distribution of a mixed spin Ising model

A mixed spin Ising system consisting of spin-1/2 and spin-3/2 with a random field is studied theoretically by the use of effective field theory with correlations (EFT). The phase diagrams and thermal behaviors of magnetization are investigated numerically for a square lattice (z = 4) when the random field is bimodally and trimodally distributed. The results show that tricritical points exist when the external random fields H and the values of p are not too large. Re-entrant phenomena can be seen for appropriate ranges of p and random fields H. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.