Magnetic and electronic properties of Eu4Sr4Ga16Ge30
Magnetization, static and ac magnetic susceptibility, nuclear forward scattering, and electrical resistivity measurements have been performed on polycrystalline Eu4Sr4Ga16Ge30, a type I clathrate that has divalent strontium and europium ions encapsulated within a Ga-Ge framework. These data are compared with those of type I clathrates Eu8Ga16Ge30 and Eu6Sr2Ga16Ge30. The ferromagnetic ordering of these Eu-containing clathrates is substantially altered by the incorporation of strontium, as compared to Eu8Ga16Ge30. Ferromagnetism, accompanied by a relatively large negative magnetoresistance, is observed below 15 and 20 K in Eu4Sr4Ga16Ge30 and Eu6Sr2Ga16Ge30, respectively. An effective magnetic moment of 7.83 μB per Eu ion is observed above 30 K for Eu4Sr4Ga16Ge30, a moment which is close to the free-ion moment of 7.94 μB per europium(II) ion.
G.T. Woods, J. Martin, M. Beekman, Raphaël P. Hermann, Fernande Grandjean, Veerle Keppens, O. Leupold, Gary J. Long, and G.S. Nolas. "Magnetic and electronic properties of Eu4Sr4Ga16Ge30" Physical Review B 72.17 (2006): 174403.
Available at: http://works.bepress.com/veerle_keppens/15