Synthesis of delafossite-derived phases, RCuO{sub 2+{delta}} with R=Y, La, Pr, Nd, Sm, and Eu, and observation of spin-gap-like behavior
- Research and Development Center, Tohoku Electric Power Company, Incorporated, 2-1 Nakayama 7-chome, Aoba-ku, Sendai 981 (Japan)
- Materials and Structures Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226 (Japan)
The structural and physical properties of layered cuprates of a RCuO{sub 2} delafossite structure have been investigated for various rare-earth elements R: Y, La, Pr, Nd, Sm, and Eu. An oxygen-rich delafossite-derived phase, RCuO{sub 2+{delta}} ({delta}{ge}0.5), as previously reported by Cava {ital et al.} for R=Y and La was found for all the other R presently studied. Each as-sintered RCuO{sub 2} sample appeared to have a nearly stoichiometric oxygen content, but by thermal oxidation excess oxygen atoms corresponding to {delta}{ge}0.5 per formula unit could be loaded into the lattices. Although electrical resistivity ({rho}) of the oxygen-rich RCuO{sub 2+{delta}} samples exhibited semiconducting behavior at temperatures below 325 K a couple of samples showed anomalous temperature dependences in {rho} at low temperatures. Unusual temperature dependence of magnetic susceptibility ({chi}), was observed for Ca-doped YCuO{sub 2+{delta}} samples, but not for the other RCuO{sub 2+{delta}} phases. If the Curie term was subtracted from the susceptibility of (Y,Ca)CuO{sub 2+{delta}}, the remaining part of {chi} decreased monotonically with decreasing temperature down to {approximately}100K, and then leveled off with a finite value. Assuming that this finite value could be attributed to the Pauli paramagnetism of free carriers, the {chi} vs T characteristics were compared with those of other layered cuprates, such as SrCu{sub 2}O{sub 3}, (Sr,Ca){sub 14}Cu{sub 24}O{sub 41}, and (La,Sr)CuO{sub 2.5}, which have been reported to exhibit spin-gap behavior. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 528111
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 56, Issue 6; Other Information: PBD: Aug 1997
- Country of Publication:
- United States
- Language:
- English
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