Ferromagnetism and accompanying large negative magnetoresistance in Pb-substituted Bi-Sr-Co-O misfit-layer compound are investigated in detail. Recent structural analysis of (Bi,Pb)2Sr3Co2O9, which has been believed to be a Co analogue of Bi2Sr2CaCu2O8+δ, revealed that it has a more complex structure including a CoO2 hexagonal layer [T. Yamamoto {\it et al.}, Jpn. J. Appl. Phys. {\bf 39} (2000) L747]. Pb substitution for Bi not only introduces holes into the conducting CoO2 layers but also creates a certain amount of localized spins. Ferromagnetic transition appears at T = 3.2 K with small spontaneous magnetization along the c axis, and around the transition temperature large and anisotropic negative magnetoresistance was observed. This compound is the first example which shows ferromagnetic long-range order in a two-dimensional metallic hexagnonal CoO2 layer.
@article{arxiv.cond-mat/0012395,
title = {Ferromagnetism and large negative magnetoresistance in Pb doped Bi-Sr-Co-O misfit-layer compound},
author = {I. Tsukada and T. Yamamoto and M. Takagi and T. Tsubone and S. Konno and K. Uchinokura},
journal= {arXiv preprint arXiv:cond-mat/0012395},
year = {2009}
}
Comments
8 pages including eps figures. To be published in J. Phys. Soc. Jpn