ISING CHAIN WITH RANDOM SHORT-RANGE AND LONG-RANGE INTERACTIONS

An tract solution is obtained for the 1D Ising model, closed chain, wi th random short-and long-range interactions satisfying bimodal anneale d distributions. The long-range interactions satisfy a strongly correl ated distribution, and the distribution of the short-range interaction s J(i) is explicitly given by (sic)(J(i)) = p delta(J(i)-J(A)) + (1 - p)delta(J(i) - J(B)). For the particular case of uniform ferromagnetic long-range interactions explicit results ale presented for the thermo dynamic functions. It is shown that for dilute antiferromagnetic or fo r competing short-range interactions the spontaneous magnetization of the system can increase with temperature. It is also shown that the ma gnetization, as a function of temperature, can exhibit discontinuities . in addition to the usual first-and second-order phase transitions sh own by the pure model (p = 0 or 1). (C) 1998 Elsevier Science B.V. All rights reserved.