title: High pressure induced spin state crossover in Sr2CaYCo4O10.5.
abstract: The layered cobaltite Sr(2)CaYCo(4)O(10.5) with formal average cobalt oxidation state close to 3+ has been studied as functions of both temperature and pressure up to 4 GPa by neutron powder diffraction (NPD). The crystal structure is shown to have tetragonal symmetry (space group I4/mmm; 2a(p) × 2a(p) × 4a(p) superstructure), and the magnetic structure at ambient pressure is found to be G-type antiferromagnetic with TN close to 310 K. The magnetic moments within the CoO(6) octahedral layers and anion-deficient CoO(4.5) layers are 1.2μ(B) and 2.8μ(B), respectively. At 25 K, and applied pressure of 3.5 GPa is sufficient to completely suppress a long-range magnetic order. This result is interpreted in terms of a pressure-induced high-to-low spin state crossover of the Co(3+) ions.
authors.affiliation: Helmholtz-Zentrum Berlin, 14109 Berlin, Germany. Joint Institute for Nuclear Research, 141980 Dubna, Russia. Institute of Applied Geosciences, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Sikolenko
authors.forename: I
authors.initials: I
authors.lastname: Troyanchuk
authors.forename: M
authors.initials: M
authors.lastname: Bushinsky
authors.forename: V
authors.initials: V
authors.lastname: Efimov
authors.forename: L
authors.initials: L
authors.lastname: Keller
authors.forename: J S
authors.initials: JS
authors.lastname: White
authors.forename: F R
authors.initials: FR
authors.lastname: Schilling
authors.forename: S
authors.initials: S
authors.lastname: Schorr