In RBaCo_{2}O_{5+x} compounds (R is rare earth), a ferromagnetic-antiferromagnetic competition is accompanied by a giant magnetoresistance. We study the magnetization of detwinned GdBaCo_{2}O_{5.5} single crystals, and find a remarkable uniaxial anisotropy of Co^{3+} spins which is tightly linked with the chain oxygen ordering in GdO_{0.5} planes. Reflecting the underlying oxygen order, CoO_2 planes also develop a spin-state order consisting of Co^{3+} 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.
翻译：在RBACO ⁇ 2}O ⁇ 5+x}化合物(R为稀土)中,一个铁磁抗反热磁性竞争伴之以巨大的磁极效应。我们研究了脱钩的GdBaco ⁇ 2}O ⁇ 5.5}单晶体的磁化,并发现了一个与GdO ⁇ 0.5}飞机上订购的链氧紧密相连的Co ⁇ 3 ⁇ 3 ⁇ ion在S=1和S=0交替行中的旋转状态。磁性结构似乎由与Ising相似的瞬间相弱相交的铁磁梯组成,为磁性迁移现象提供了简单图片。
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