FINITE-SIZE-SCALING ON RANDOM MAGNETIC-STRUCTURES

We study the ferromagnetic Ising model on very long strips of random w idths using transfer matrix techniques. The width distribution is Gaus sian with mean L and rms deviation Delta L, which may be constant for any L (type I) or proportional to L (type II). We calculate the initia l susceptibility for strips with 4 less than or equal to L less than o r equal to 12, obtaining estimates of the ratio of exponents (gamma/nu )(L) and the pseudocritical temperature T(L,L - 1). In strips of type I, those estimates satisfy finite-size scaling, with finite-size corr ections increasing with Delta L, and in strips of type II it is satisf ied only for very large lengths L. We discuss the influence of nonunif orm thicknesses on the magnetism of low-dimensional systems, comparing the finite-size corrections of this problem to those which fit the ex perimental data of magnetic thin films.