Inter-network magnetic interactions in GdMexMn1−xO3 perovskites (Me=transition metal)

The gadolinium-based manganite GdMnO₃ of perovskite structure has been partially substituted at the manganese site by transition metal elements Me like Cu, Ni and Co, leading to a general formula GdMe_xMn_1−xO₃, in which different magnetic entities (e.g., Gd³⁺, Cu²⁺, Ni²⁺, Co²⁺, Co³⁺, Mn³⁺, Mn⁴⁺) can coexist, depending on charge equilibrium conditions. For divalent cations such as Cu²⁺ and Ni²⁺, the solid solution extends from x  (Me)=0–0.5, with O-type orthorhombic symmetry (a(a<c/√2<b). When the substituting element is cobalt, the solid solution extends over the whole range [0?x  ?1], changing from O′-type symmetry (c/√2(c/√2<a<b) to O-type for x>0.5. In this latter case, the synthesis is performed under oxygen flow, which allows the cobalt ion to take a 3+ oxidation state.