Magnetic Structures of High Temperature Phases of TbBaCo_2O_<5.5> (Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite TbBaCo_2O_<5.5> in the temperature range of 7-370 K. There have been observed several magnetic or structural transitions. Among these, the existence of the transitions to the insulating phase from the metallic one at 〜340 K, to the one with the ferromagnetic moment at 〜280 K and possibly to the antiferromagnetic one at 〜260 K, with decreasing temperature T correspond to those reported in former works. We have studied the magnetic structures at 270 K and 250 K and found that all Co^<3+> ions of the CoO_6 octahedra are in the low spin state and those of the CoO_5 pyramids carry spins which are possibly in the intermediate spin state. Non-collinear magnetic structures are proposed at these temperatures. Two other transitions have also been observed at the temperatures, 〜100 K and 〜250 K.
社団法人日本物理学会の論文
2003-07-15