Magnetic phase evolution in the spinel compounds Zn(1-x)Co(x)Cr(2)O(4).

We present the magnetic properties of complete solid solutions of ZnCr(2)O(4) and CoCr(2)O(4): two well studied oxide spinels with very different magnetic ground states. ZnCr(2)O(4), with non-magnetic d(10) cations occupying the A site and magnetic d(3) cations on the B site, is a highly frustrated antiferromagnet. CoCr(2)O(4), with magnetic d(7) cations (three unpaired electrons) on the A site as well, exhibits Néel ferrimagnetism as well as commensurate and incommensurate non-collinear magnetic order. More recently, CoCr(2)O(4) has been studied extensively because of its polar behavior which arises from conical magnetic ordering. Gradually introducing magnetism on the A site of ZnCr(2)O(4) results in a transition from frustrated antiferromagnetism to glassy magnetism at low concentrations of Co, and eventually to ferrimagnetic and conical ground states at higher concentrations. Real-space Monte Carlo simulations of the magnetic susceptibility suggest that the first magnetic ordering transition and features of the susceptibility across x are captured by near-neighbor self-couplings and cross-couplings between the magnetic A and B atoms. We present, as a part of this study, a method for displaying the temperature dependence of magnetic susceptibility in a manner which helps distinguish between compounds possessing purely antiferromagnetic interactions from compounds where other kinds of ordering are present.