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 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× 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.
Highlights
The values of the strong coupling ratio (2¢/kTc) shown here were obtained using the indicated methods of gap measurement
The persistence of ¢p above Tc in the underdoped regime is in good agreement with a decrease of the spin susceptibility below a temperature Tp
A non-mean-®eld behaviour may just indicate the presence of strong phaseuctuations, and not necessarily the presence of preformed pairs in the Mott sense[23]. Both local pairs and the stripe model may explain the continuous increase of ¢p in the underdoped regime
Summary
The values of the strong coupling ratio (2¢/kTc) shown here were obtained using the indicated methods of gap measurement (see text for details). Title High-temperature weak ferromagnetism in a low-density free-electron gas. Powered by the California Digital Library University of California letters to nature
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