Critical exponents and magnetic short-range order in the system CdCr2xIn2-2xS4

High temperature series expansions are derived for the magnetic susceptibil ity and two-spin correlation functions for a Heisenberg ferromagnetic model on the B-spinel lattice, The calculations are done in the framework of the random phase approximation and are given for both nearest and next-nearest neighbour exchange integrals J(1) and J(2), respectively. Our results are given up to order six in beta = (k(B)T)(-1) and are used to study the param agnetic region of the ferromagnetic spinel CdCr2xIn2-2xS4. Thr critical tem perature T-c and the critical exponents gamma and nu associated with the ma gnetic susceptibility chi (T) and the correlation length xi (T), respective ly, are deduced by applying the Pade approximant methods. The results as a function of the dilution x obtained by the present approach are found to be in excellent agreement with the experimental ones and can be compared with other theoretical studies based on the 3D Heisenberg model.