title: Microscopic evidence of spin state order and spin state phase separation in layered cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho.
abstract: We report muon-spin relaxation measurements on the magnetic structures of RBaCo2O(5.5) with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co3+ of CoO6 octahedra. Phase separation into well separated regions with different spin state order is observed in the antiferromagnetic phases. The unusual strongly anisotropic magnetoresistance and its onset at the FM-AFM phase boundary is explained.
authors.affiliation: Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland. hubertus.luetkens@psi.ch
authors.forename: H
authors.initials: H
authors.lastname: Luetkens
authors.forename: M
authors.initials: M
authors.lastname: Stingaciu
authors.forename: Yu G
authors.initials: YG
authors.lastname: Pashkevich
authors.forename: K
authors.initials: K
authors.lastname: Conder
authors.forename: E
authors.initials: E
authors.lastname: Pomjakushina
authors.forename: A A
authors.initials: AA
authors.lastname: Gusev
authors.forename: K V
authors.initials: KV
authors.lastname: Lamonova
authors.forename: P
authors.initials: P
authors.lastname: Lemmens
authors.forename: H-H
authors.initials: HH
authors.lastname: Klauss