Structure and Magnetic Susceptibility of Mn11Ta4O21and Refinement of the Mn4Ta2O9Structure

✍ Scribed by J Grins; A Tyutyunnik

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 362 KB
• Volume: 137
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1997.7733

✦ Synopsis

The structure of Mn 11 Ta 4 O 21 has been determined and refined using the Rietveld method with combined CuK 1 X-ray and time-of-flight neutron powder data in space group P3 c1 to R F 2 ‫؍‬ 1.3% (neutron data) and R F 2 ‫؍‬ 7.8% (X-ray data). The unit cell is a ‫؍‬ 5.3776(2) A s , c ‫؍‬ 34.040(2) A > , V ‫؍‬ 852.5 A > 3 , and Z ‫؍‬ 2. The structure consists of a 14-layer hexagonal sequence of close packed oxygen atoms and an ordered distribution of metal atoms in octahedral coordination. It can be described as built up of corundum-type Mn 4 Ta 2 O 9 blocks, with six layers of octahedra, alternating with single MnO layers of octahedra. The structure is compared with that of corundum-related Mn 4 Ta 2 O 9 , with unit cell a ‫؍‬ 5.3306(2) A s , c ‫؍‬ 14.336(1) A s , V ‫؍‬ 352.8 A s 3 , and Z ‫؍‬ 2, which has been refined in space group P3 c1 to R F 2 ‫؍‬ 1.9%, using constant-wavelength ( ‫؍‬ 1.47 A > ) neutron powder diffraction data. The magnetic susceptibility of Mn 11 Ta 4 O 21 exhibits a maximum at 23 K and a Curie-Weiss behavior at higher temperatures with a ‫؍‬ ؊240 K and eff ‫؍‬ 5.7 B per Mn atom.