Temperature-independent ytterbium valence in YbGaGe

Negative thermal expansion in functional materials: controllable thermal expansion by chemical modifications

“…279 As shown in Fig. [282][283][284][285][286][287] The charge variation of Yb was not observed and is nearly divalent in YbGaGe. 279 NTE of RE 2.75 C 60 can be adjusted by various rare earths.…”

“…45, at high temperatures, 4f electrons can be thermally excited from the narrow 4f band into the C 60 t 1u band; while at low temperatures, these electrons are taken back into the 4f band resulting in a 4f 14 Yb electronic configuration and an expanded ionic radius. [285][286][287] The low thermal expansion in YbGaGe could be resulted from the doping of carbon impurities. For example, Sm 2.75 C 60 and Yb 2.75 C 60 exhibit NTE with a V = À4.0 Â 10 À4 K À1 (r 32 K) and a V = À5.5 Â 10 À4 K À1 (r32 K), respectively.…”

Electronic structure of YbGa1.15Si0.85and YbGaYamaoka1, Jarrige2, Tsujii3 et al. 2011Phys. Rev. B

“…No temperature dependence is observed for both PFY-XAS and RXES spectra, and accordingly for the valence, from room temperature down to 7 K within an accuracy of a few %. Doyle et al 20 13 ) with pressure as observed in Yb metal. 37 But at present we do not understand why Yb valence saturates around v∼2.55.…”

“…Note that although we measure the YbGa 1.1 Ge 0.9 sample with similar chemical composition to YbGa 1. 15 20 for YbGaGe and the ones obtained from our RXES measurement.…”

“…Several authors reported the magnetic and electronic properties of YbGaGe. [14][15][16][17][18][19][20] By XAS the Yb valence of YbGaGe was found to be nearly divalent and constant with temperature. 21 Such temperature dependence of the electronic structure for YbGaSi has not been explored yet, nor the pressure dependence.…”