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Ferromagnetism and large negative magnetoresistance in Pb doped Bi-Sr-Co-O misfit-layer compound

I. Tsukada·T. Yamamoto·M. Takagi·T. Tsubone·S. Konno·K. Uchinokura
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Abstract

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)${}_2$Sr${}_{3}$Co${}_2$O${}_9$, which has been believed to be a Co analogue of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+δ}$, revealed that it has a more complex structure including a CoO${}_2$ 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 CoO${}_2$ 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 CoO${}_2$ layer.

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I. Tsukada, T. Yamamoto, M. Takagi, T. Tsubone, S. Konno, K. Uchinokura. 2000-12-21. Ferromagnetism and large negative magnetoresistance in Pb doped Bi-Sr-Co-O misfit-layer compound. https://doi.org/10.1143/jpsj.70.834

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