The magnetic state of diamagnetically diluted antiferromagnetic cobalt and nickel monoxide

Abstract The nearest neighbour J 1 ( x ) and the next-neighbour super-exchange J 2 ( x ) interactions are evaluated by using the mean field theory for Mg 1 − x B x O ( B = Co and Ni) systems. The magnetic energy E ( x ) is obtained. A magnetic phase diagram of the Mg 1 − x B x O ( B = Co and Ni) solid solutions with 0 ⩽ x ⩽ 1 is drawn by high-temperature series expansions (HTSE) combined with the Pade approximants method (PA). The critical exponents associated with the magnetic susceptibility ( γ ) and with the correlation length ( ν ) are deduced in order phase.