Metamagnetism in the perovskite compound Gd₂CoMnO₆

Abstract The compound Gd2CoMnO6 crystallizes with the orthorhombic perovskite structure and is isomorphous with GdFeO3. A crystal structure refinement shows that the Mn3+-O2−-Mn3+ bond angles are ∼ 145° and that the distortion from cubic symmetry is considerable. A spontaneous moment of 5 e.m.u./g develops below 115°K due to the exchange interactions between near neighbouring Mn3+ ions. Below 115°K a field induced metamagnetic transition to a state with a moment of 20 e.m.u./g is also observed and this transition is depressed in temperature by 1°c for 360 oe applied field. The metamagnetism is accounted for on the basis of a transition between an uncompensated anti-ferromagnetic and a ferromagnetic state which is observed in Gd2CoMnO6 due to a change in sign of the Mn3+-O2−-Mn3+ exchange interaction originating from Jahn-Teller electronic ordering in Mn3+ ions. This ordering is favoured at low temperatures and introduces a negative contribution to the exchange interaction.