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High-temperature weak ferromagnetism in a low-density free-electron gas

Nature volume 397, pages 412–414 (1999)Cite this article

Abstract

The magnetic properties of the ground state of a low-density free-electron gas in three dimensions have been the subject of theoretical speculation and controversy for seven decades1. Not only is this a difficult theoretical problem to solve, it is also a problem which has not hitherto been directly addressed experimentally. Here we report measurements on electron-doped calcium hexaboride (CaB6) which, we argue, show that—at a density of 7× 1019 electrons cm−3—the ground state is ferromagnetically polarized with a saturation moment of 0.07 µB per electron. Surprisingly, the magnetic ordering temperature of this itinerant ferromagnet is 600 K, of the order of the Fermi temperature of the electron gas.

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Figure 1: Temperature dependences of the electrical resistivities of La-doped CaB6.
Figure 2: Magnetization per mol of compound versus applied field for La-doped CaB6, measured at 5 K (fu., formula unit).
Figure 3: Saturation moment at T = 5 K per mol La as a function of La concentration in CaB6.
Figure 4: Magnetization of Ca0.995La0.005B6 in a fixed applied field of 0.1 T as a function of temperature.

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Acknowledgements

Z.F. thanks E. Abrahams, G. Aeppli, L. Gor'kov, P. Kumar, E. Manousakis, G. Ortiz and D. Pines for discussions. Work at NHMFL was supported by the NSF; work at Los Alamos was done under the auspices of the US Department of Energy; and the work at ETH Zürich was supported by the Schweizerische Nationalfonds zur Förderung der wissenschaftlichen Forschung.

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Authors and Affiliations

  1. NHMFL, Florida State University, Tallahassee, 32306, Florida, USA

    D. P. Young, D. Hall, M. E. Torelli & Z. Fisk

  2. Material Science and Technology Division, Los Alamos National Laboratory, Los Alamos, 87454, New Mexico, USA

    Z. Fisk, J. L. Sarrao & J. D. Thompson

  3. Laboratorium fr Festkperphysik, ETH-Hnggerberg, CH-8093, Zrich, Switzerland

    H.-R. Ott

  4. Department of Physics, San Diego State University, San Diego, 92182, California, USA

    S. B. Oseroff

  5. Department of Physics, Louisiana State University, Baton Rouge, 70803, Louisiana, USA

    R. G. Goodrich

  6. Centro Atomico Bariloche, Bariloche, RN 8400, Argentina

    R. Zysler

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  1. D. P. Young
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  10. R. Zysler
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Correspondence to Z. Fisk.

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Young, D., Hall, D., Torelli, M. et al. High-temperature weak ferromagnetism in a low-density free-electron gas. Nature 397, 412–414 (1999). https://doi.org/10.1038/17081

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