Structural aspects and antiferromagnetic ordering in the {open_quotes}123{close_quotes} derivative LnSr{sub 2}Cu{sub 2}Ga{sub 1-x}Fe{sub x}O{sub 7-{sigma}} (Ln = Y, Ho)
- Universite de Caen (France); and others
The magnetic ordering in the orthorhombic phases LnSr{sub 2}Cu{sub 2}Ga{sub 1-x}Fe{sub x}O{sub 7}(Ln=Y, Ho; 0.03 {le}x{le}0.95) has been investigated by {sup 57}Fe Moessbauer spectroscopy. Iron occupies the Ga site (Cu(1) site) for small doping rates (x {approx} 0.03), but occupies the Cu(1) and Cu(2) sites for iron-rich compositions (0.5{le}x{le}0.95). For x = 0.9, the magnetic ordering takes place below T{sub N} {approx} 420 K in both the Cu(1) and Cu(2) sites. The down concave curve of the temperature dependence of the hyperfine field in the Cu(1) site suggests a rather weak coupling between the Cu(1) and Cu(2) sites. The principal EFG axis V{sub ZZ} is directed in both sites along the longest axis of the orthorhombic cell, i.e., perpendicular to the longest axis of the orthorhombic cell, i.e., perpendicular to the alternating sheets. The sign of V{sub ZZ} is positive for the Cu(2) sites ({delta}E{sub Q} = 0.6 mm/sec) and negative for the Cu(1) sites ({delta}E{sub Q}= -1.9 mm/sec). In the distorted tetrahedral site, the EFG tensor is non-axial, however, its asymmetry is small ({eta} < 0.4). The magnetic hyperfine field is perpendicular to the V{sub ZZ} axis for both sites; i.e., H lies in the plane of the shortest axes. A structural analysis by electron microscopy reveals the presence of a large number of defects in the (Fe, Ga)O chain ordering as well as in the basic structure. The presence and the abundance of these defects is in agreement with the Moessbauer observations.
- OSTI ID:
- 508643
- Journal Information:
- Journal of Solid State Chemistry, Vol. 113, Issue 1; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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