MAGNETIC-STRUCTURE AND GROUND-STATES IN SPINEL B-SITE LATTICE

The ground states of diluted spinel AB(2x)B'(2-2x)-X(4) are studied as a function of x in the range 0.85 less than or equal to x less than o r equal to 1 by means of a classical minimization of the exchange ener gies taking into account exchange integrals up to the fourth nearest n eighbors J(4). At low temperature, the magnetic structure observed in the spinel solid solution ZnCr2xAl2-2xS4 is well represented in the ob tained ground states. The values of the relative exchange integrals, t he intraplanar and the interplanar interactions are deduced. The disap pearance of the long-range order is shown to be due to the decrease of the relative interplanar and intraplanar interactions when diluting C r by Al.