The Layered Manganate Sr4-xBaxMn3O10: Synthesis, Structural and Magnetic Properties.

Abstract The layered manganate Sr 4 Mn 3 O 10 has been synthesized and a partial substitution of Ba for Sr, leading to the solid solution Sr 4− x Ba x Mn 3 O 10 with 0≤ x ≤2.50, has been shown. This phase, isotypic to Ba 4 TiPt 2 O 10 , crystallizes in the Cmca space group with a =5.4766(1) A, b =12.4659(2) A, c =12.5282(2) A for x =0. The structural analysis of this oxide shows close relationships with the 9 L-hexagonal BaMnO 3 structure, both structures being built up from ‘Mn 3 O 12 ’ trioctahedral units of face sharing octahedra, linked through their apices. The main difference between the two structures concerns the relative orientation of two successive Mn 3 O 12 groups, leading to a layered structure for Sr 4 Mn 3 O 10 and to a tridimensional framework for 9 L-BaMnO 3 . The detailed HREM study shows the existence of extended defects, mainly along (010), which correspond to shearing mechanisms and suggests the possible existence of other original members. These oxides show an antiferromagnetic transition at T N =210–215 K.