Structural and magnetic properties of the solid solution (0 < = x<=1) Ymn_(1-x)(Cu_(3/4)MO_(1/4))_xO_3

摘要

Recently, the ferroelectromagnet YM_xO_3 has been the focus of interest because it exhibits both antiferromagnetism (Neel temperature ~ 80 K) and ferroelectricity (Curie temperature ~ 914 K). There have been BO reports of complete Ymn_(1-x)(Cu_(3/4)MO_(1/4))_xO_3solid solutions in which substitution of the foreign M cation preserves the hexagonal P63C111 structure. In contrast there exist several homeotypic phases with the general formula, Ymn_(1-x)(Cu_(3/4)MO_(1/4))_xO_3 (n = 1 (M = Ti), 2 (M = V) and 3 (M = Mo); Ln: lanthanide). Several Ymn_(1-x)(Cu_(3/4)MO_(1/4))_xO_3 compounds have been synthesized. The solid solution, from YmnO_3 (x = 0) to Ymn_(1-x)(Cu_(3/4)MO_(1/4))_xO_3 (x = 1) has been characterized by X-ray diffraction and transmission electron microscopy study. For 0 < x < 0.9, the compounds are found to crystallize in the non-centrosymmetric structure, space group P63c.n1, of YmnO_33. The Mn-free end member, x = 1, crystallizes in a complex multiple cell, the superstructure being associated to Cu~(3+)/Mo~(6+) cationic ordering. Dilution of the Mn~(3+) magnetic array by the paramagnetic (Cu~(2+)) and diamagnetic (Mo~(6+)) cations is found to decrease the antiferromagnetic ordering temperature and it becomes undetectable for x > = 0.5 compositions.