No abstract

No abstract

No abstract

No abstract

Single crystals of pure and carbon-substituted divalent hexaborides EuB 6 and YbB 6 have been prepared by the Al flux method. Lattice parameters, density measurements, and microprobe analysis show that the single crystals are very close to stoichiometry, EuB 6 is ferromagnetic (Tc = 12.S K and ()p = IS K) while YbB 6 is diamagnetic. Resistivity and Hall effect measurements carried out over a wide temperature range show that both pure hexaborides are semiconductors with a small intrinsic gap. The carbon-substituted hexaborides RE B6 _ x ex (RE = Eu, Yb) have a metallic behavior due to the donation of electrons to the conduction band by carbon atoms. Metallic conduction, at low temperature, in the "pure" hexaborides is attributed to the formation of an impurity band containing more than 10 18 electrons per cm 3 •

No abstract

No abstract

No abstract