Fermi-surface measurements on the low-carrier density ferromagnet Ca1-xLaxB6 and SrB6 -: art. no. 233105

Recently it has been discovered that weak ferromagnetism of a dilute three-dimensional electron gas develops on the energy scale of the Fermi temperature in some of the hexaborides; that is, the Curie temperature approximately equals the Fermi temperature. We report the results of de Haas-van Alphen experiments on two concentrations of La-doped CaB6 as well as Ca-deficient Ca1-deltaB6 and Sr-deficient Sr1-deltaB6. The results show that a Fermi surface exists in each case and that there are significant electron-electron interactions in the low-density electron gas.