Neutron and X-ray powder diffraction study of RBa{sub 2}Fe{sub 3}O{sub 8+w} phases

Journal Article · Sun Feb 15 00:00:00 EST 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1997.7636· OSTI ID:642193

Karen, P; Kjekshus, A ^[1]; Huang, Q ^[2]; Lynn, J W; Rosov, N; Sora, I N; Karen, V L; Mighell, A D; Santoro, A ^[3]

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1. Univ. of Oslo, Blindern, (Norway). Dept. of Chemistry
2. Univ. of Maryland, College Park, MD (United States)
3. National Inst. of Standards and Technology, Gaithersburg, MD (United States). Reactor Radiation Div.

Compounds of composition RBa{sub 2}Fe{sub 3}O{sub 8+w} (R = La, Nd, Sm, Gd, Dy, Er, Yb, Lu, and Y) with variable oxygen content have been synthesized using the liquid mixing technique and have been analyzed by powder X-ray and neutron diffraction methods. A triple perovskite-type structure with ordered Ba and R cations and having the symmetry of space group P4/mmm was obtained only for R = Y, Dy, and Er, whereas the larger R atoms gave the atomic arrangement of disordered, defective perovskites with average symmetry Pm{bar 3}m. No perovskite-type phases were obtained when Yb and Lu were tried. The oxygen content of the oxygen-saturated phases was found to increase with increasing size of the cation R from w = 0.07 for Er to w = 0.83 for La. The Neel temperature ({approximately}650 K) and the magnitude of the Fe magnetic moment ({approximately}3.3 {mu}{sub B} at room temperature) are highest when trivalent iron is involved (w = 0), but these quantities are rather insensitive to the nature of R and to slight variations of oxygen content in the triple perovskite-type structure of the Y, Dy, and Er compounds. In the case of the cubic structures, however, both quantities depend strongly on the oxygen stoichiometry. In the magnetically ordered state, nearest-neighbor iron moments are coupled antiferromagnetically along the three crystallographic directions in all samples, resulting in magnetic structures with symmetry Imm{prime}m and magnetic unit cells related to those of the corresponding nuclear structures by the transformation matrix (1{bar 1}0/110/002).

• OSTI ID: 642193
• Journal Information: Journal of Solid State Chemistry, Vol. 136, Issue 1; Other Information: PBD: 15 Feb 1998
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL STRUCTURE
RARE EARTH COMPOUNDS
OXIDES
BARIUM OXIDES
IRON OXIDES
PEROVSKITES
NEUTRON DIFFRACTION
X-RAY DIFFRACTION
LATTICE PARAMETERS
EXPERIMENTAL DATA