The cooperative Jahn-Teller effect in BaFe2.5Mn9.5O19

✍ Scribed by Z. Jirák; E. Pollert; S. Vratislav

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 437 KB
• Volume: 183
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/0921-4526(93)90059-f

✦ Synopsis

The distorted magnetoplumbite-type structure of BaFe2SMng.s019 has been studied by powder neutron diffraction.

The compound is orthorhombic, space group Cmcm (a = 5.826 A, b = 10.367 A, c = 23.004 A, Z = 4). Manganese is substituted into all five iron sites of the barium ferrite with popUlation decreasing when going from the centre of the S block (100% of Mn for the 2a site) to the centre of the R block (40% for the 4e(I/2) site). The structure includes two types of local Jahn~ Teller distortions ~ the shortened Mn 3 + 0 6 octahedra in sites 4fvI and two thirds of sites 12k and the elongated octahedra in the remaining third. Manganese in the tetrahedral site 4f IV is bivalent and is compensated by Mn4+ ions located preferentially in the octahedral site 2a. Ferrimagnetic arrangement below Tc = 220 K involves a large deal of static disorder. The ordered moments are aligned along the c-axis.