Influence of the non-magnetic cation upon the sign of the CrIII–CrIII coupling in trirutile compounds MCr2O6(M = Te, W)

Abstract

We report on the magnetic susceptibility of TeCr₂O₆ and WCr₂O₆ in the temperature range 4.2–350 K in the light of crystal structure and neutron diffraction results. The susceptibility mainly results from the cationic ordering between magnetic and non-magnetic ions which leads to (Cr₂O₁₀)^14– units. The magnetic interaction described by the Heisenberg model and the experimental data are in good agreement with predicted values if we take J=–33.2 K and J=–44.5 K for the exchange constants of TeCr₂O₆ and WCr₂O₆, respectively; these values are correlated with structural variations. In the low temperature range, the nature of the non-magnetic ion plays a major role since the intercluster coupling is either ferromagnetic (W) or antiferromagnetic (Te). The corresponding values of the exchange (1.4 and –4.5 K, respectively) are determined and discussed via the molecular field approximation.