title: Neutron diffraction studies of structural and magnetic properties of niobium doped cobaltites.
abstract: Neutron powder diffraction studies of the structural and magnetic properties of the La(1-x)Sr(x)Nb(y)Co(1-y)O(3) solid solutions (x = 0.2, 0.5; y = 0, 0.075, 0.1) have been performed. Substitution of Co(2+) by Nb(5+) prevents the formation of Co(4+) and leads to stabilization of the Co(3+) ions in the high- or intermediate-spin state. This is accompanied by the significant change of the Co-O bond length as well as Co-O-Co bond angle in the CoO(6) octahedron. The obtained data are in agreement with the negative sign of the magnetic exchange interactions Co(3+)-O-Co(3+) in a relatively wide range of the Co-O-Co bond angles. Diamagnetic dilution by the niobium ions prevents long-range magnetic ordering and strongly increases magnetoresistance at low temperature.
authors.affiliation: Laboratory of Neutron Scattering, ETH Zürich and Paul Scherrer Institute, Villigen, CH-5232, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Sikolenko
authors.forename: V
authors.initials: V
authors.lastname: Efimov
authors.forename: E
authors.initials: E
authors.lastname: Efimova
authors.forename: A
authors.initials: A
authors.lastname: Sazonov
authors.forename: C
authors.initials: C
authors.lastname: Ritter
authors.forename: A
authors.initials: A
authors.lastname: Kuzmin
authors.forename: I
authors.initials: I
authors.lastname: Troyanchuk