Enhancement of the Curie temperature in NdBaCo$_{2}$O$_{5.5}$ by Ca substitution

ORAL

Abstract

RBaCo$_{2}$O$_{5.5}$ (R=rare earth or Y) undergoes a sequence of magnetic and electronic transitions between antiferromagnetic/ferrimagnetic/paramagnetic and insulating/paramagnetic metallic states with respective transition temperatures T$_{N}$(230-260 K)$<$T$_{C}$(250-290 K)$<$T$_{MI}(\sim $360 K). We have synthesized a Nd$_{1-x}$Ca$_{x}$BaCo$_{2}$O$_{5.5}$ series (0$\le $x$\le $0.2) of cation- [(Nd,Ca)/Ba] and oxygen vacancy ordered materials and investigated them by neutron diffraction, magnetization, electronic and thermal transport. We observe that upon Ca doping T$_{N}$ is decreasing to 0 for x=0.1 and T$_{C}$ is increasing and coincides with T$_{MI}$ for x$>$0.12, which weakly changes with Ca substitution from $\sim $360 to $\sim $340 K. This is the largest enhancement of T$_{C}$ ever observed for these cobaltites. Unlike the hole doping by adding oxygen, the Ca doping does not disrupt the cation and oxygen vacancy orderings up to x=0.2.

*Work at NIU was supported by the NSF (DMR-0706610) and at ANL by the U.S. DOE under contract No. DE-AC02-06CH11357.

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Authors

  • S. Kolesnik

    • Physics Department, Northern Illinois University, DeKalb, IL 60115
    • Department of Physics, Northern Illinois University, DeKalb, IL and Materials Science Division, Argonne National Laboratory, Argonne, IL
    • Physics Department, Northern Illinois University, DeKalb IL 60115
    • Department of Physics, Northern Illinois University, DeKalb, IL 60115

  • B. Dabrowski

    • MSD, Argonne National Laboratory, and Physics, Northern Illinois University, De Kalb IL, USA
    • Physics Department, Northern Illinois University, DeKalb, IL 60115
    • Physics Department, Northern Illinois University, DeKalb, IL 60115 and Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
    • Department of Physics, Northern Illinois University, DeKalb, IL and Materials Science Division, Argonne National Laboratory, Argonne, IL
    • Northern Illinois University
    • Physics Department, Northern Illinois University, DeKalb IL 60115
    • Department of Physics, Northern Illinois University, DeKalb, IL 60115

  • O. Chmaissem

    • MSD, Argonne National Laboratory, and Physics, Northern Illinois University, De Kalb IL, USA
    • Physics Department, Northern Illinois University, DeKalb, IL 60115
    • Physics Department, Northern Illinois University, DeKalb, IL 60115 and Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
    • Department of Physics, Northern Illinois University, DeKalb, IL and Materials Science Division, Argonne National Laboratory, Argonne, IL
    • Department of Physics, Northern Illinois University, DeKalb, IL 60115

  • K. Swierczek

    • Materials Science Division, Argonne National Laboratory, Argonne, IL and University of Science and Technology, Krakow, Poland