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 decades. 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 x 1019 electrons cm-3 - the ground state is ferromagnetically polarized with a saturation moment of 0.07 μ(B) 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.
Publication Source (Journal or Book title)
Young, D., Hall, D., Torelli, M., Fisk, Z., Sarrao, J., Thompson, J., Otto, H., Oseroff, S., Goodrich, R., & Zysler, R. (1999). High-temperature weak ferromagnetism in a low-density free-electron gas. Nature, 397 (6718), 412-414. https://doi.org/10.1038/17081