A-site Randomness Effect on Structural and Physical Properties of Ba-based Perovskite Manganites(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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The discovery of novel structural and physical properties in the A-site ordered manganite RBaMn_2O_6 (R = Y and rare earth elements) has demanded new comprehension about perovskite manganese oxides. In the present study, the A-site disordered form, R_<0.5>Ba_<0.5>MnO_3, has been investigated and compared with both RBaMn_2O_6 and R_<0.5>A_<0.5>MnO_3 (A : Sr, Ca) in the structures and electromagnetic properties. R_<0.5>Ba_<0.5>MnO_3 has a primitive cubic perovskite cell in the structure and magnetic glassy states are dominant as its ground state, in contrast to the ordinary disordered R_<0.5>A_<0.5>MnO_3 (A: Sr, Ca). In Prcompounds with various degrees of Pr/Ba randomness at the A-sites, the A-site disorder gradually suppresses both ferromagnetic and A-type antiferromagnetic transitions and finally leads to a magnetic glassy state in Pr_<0.5>Ba_<0.5>MnO_3. A peculiar behavior, multi-step magnetization and resistivity change, has been observed in Pr_<0.5>Ba_<0.5>MnO_3. These properties could be closely related to any spatial heterogeneity caused by the random distribution of Ba^<2+> and R^<3+> with much different ionic radius.
社団法人日本物理学会の論文
2004-08-15