Abstract
Single-phase samples of Yb 4LiGe 4 and Yb 5Ge 4 were synthesized using high frequency (HF) heat treatment. Yb 4LiGe 4 crystallizes in orthorhombic space group Pnma with the Gd 5Si 4 type of crystal structure and lattice parameters a = 7.0828(3) Å, b = 14.6415(7) Å, and c = 7.6279(4) Å. One Yb position in Yb 5Ge 4 is substituted by the lithium atom and causes a distortion of the germanium tetragons in Yb 4LiGe 4. Investigation of the electronic state of Yb via magnetic susceptibility and X-ray absorption near-edge spectroscopy (XANES) revealed a presence of two electronic states of ytterbium, 4 f 13 and 4 f 14 (mixed valence), in Yb 5Ge 4 and Yb 4LiGe 4. Studies of the temperature dependence of the electrical resistivity, magnetization, 7Li spin-lattice relaxation rate and the specific heat indicate that strong electronic correlations are present in Yb 4LiGe 4, and below approximately 50 K there is a competition between ferromagnetic and antiferromagnetic correlations. Magnetic ordering in Yb 4LiGe 4, if present, occurs below the reported antiferromagnetic transition temperature of 1.7 K for Yb 5Ge 4.
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