title: Two-dimensional magnetic clusters in La(n)(Ti(1-x)Fe(x))(n)O(3n+2) (n = 5 with x = 0.2 and n = 6 with x = 0.33).
abstract: Crystal structure analyses of the layered compounds La(n)(Ti(1-x)Fe(x))(n)O(3n+2), with nominal compositions x = 0.2 for n = 5 and x = 0.33 for n = 6, show that the iron is concentrated at the centers of the slabs. The spatial arrangements of the iron ions can be approximated by two-dimensional square lattices with strong magnetic interactions between neighboring sites, albeit with fractional occupancies of the sites of an average of 0.67 magnetic ions in n = 6 and 0.42 magnetic ions in n = 5 compounds. A previously described (Lichtenberg et al 2008 Prog. Solid State Chem. 36 253) crossover of magnetic behavior of n = 6 at room temperature is explained by the formation of two-dimensional, ferromagnetically organized magnetic clusters with an average size of 52 Fe(3+) ions. The absence of long-range magnetic order follows from the fractional occupancy of the sites by the magnetic ions. The lower concentration of magnetic ions in n = 5 explains why crossover behavior is not found and clusters do not form in that compound.
authors: Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth, Germany.
authors: Alexander
authors: A
authors: Wölfel
authors: Frank
authors: F
authors: Lichtenberg
authors: Sander
authors: S
authors: van Smaalen
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D060526:Magnetic Fields; D008422:Materials Testing; D008968:Molecular Conformation; D010087:Oxides / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D010087:Oxides; C009495:titanium dioxide; C000499:ferric oxide; C103829:lanthanum oxide; D007811:Lanthanum; D014025:Titanium