Abstract
Using the high-temperature series expansion method the critical temperature and critical index gamma for a system consisting of a random mixture of Ising and Heisenberg couplings have been estimated. It has been found that gamma as a function of concentration p of Heisenberg-type bonds has a minimum the location of which depends strongly on the ratio of the Ising to Heisenberg coupling constants. It is conjectured that this might correspond to a change in the character of the transition.