title: Ising-like spin anisotropy and competing antiferromagnetic-ferromagnetic orders in GdBaCo2O5.5 single crystals.
abstract: In RBaCo2O5+x compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo2O5.5 single crystals and find a remarkable uniaxial anisotropy of Co3+ spins which is tightly linked with the chain oxygen ordering in GdO0.5 planes. Reflecting the underlying oxygen order, CoO2 planes also develop a spin-state order consisting of Co3+ ions in alternating rows of S=1 and S=0 states. The magnetic structure appears to be composed of weakly coupled ferromagnetic ladders with Ising-like moments, which gives a simple picture for magnetotransport phenomena.
authors.affiliation: Central Research Institute of Electric Power Industry, Komae, Tokyo 201-8511, Japan.
authors.forename: A A
authors.initials: AA
authors.lastname: Taskin
authors.forename: A N
authors.initials: AN
authors.lastname: Lavrov
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ando