A-site Randomness Effect on Structural and Physical Properties of Ba-based Perovskite Manganites

T. Nakajima; H. Yoshizawa; Y. Ueda

doi:10.1143/JPSJ.73.2283

paper

A-site Randomness Effect on Structural and Physical Properties of Ba-based Perovskite Manganites

arXiv:cond-mat/0406505 · doi:10.1143/JPSJ.73.2283

Abstract

The discovery of novel structural and physical properties in the $A$ -site ordered manganite $R$ BaMn $_{2}$ O $_{6}$ ( $R$ = 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 $R$ BaMn $_{2}$ O $_{6}$ 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 Pr-compounds 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.

9 pages, to be published in J. Phys. Soc. Jpn. 73 Aug. (2004)