Synthesis and Chemical Tuning in Intermediate Valence YbBi₂

In a previous study, YbBi₂ was reported to exhibit intermediate valence between the magnetic Yb³⁺ and nonmagnetic Yb²⁺ ions, favoring the latter of the two. This raises the question of whether it is possible to alter this behavior through some tuning parameter to achieve a quantum critical point where interesting properties may arise such as unconventional superconductivity. In this presentation, we will showcase our efforts to do this through chemical substitution of bismuth with antimony to apply chemical pressure to YbBi₂, thus leading to a decrease in it’s unit cell volume. Following trends seen in the Doniach phase diagram for Yb based compounds, a compression in the unit volume cell is expected to be correlated with a rise in RKKY interactions while the Kondo hybridization strength weakens, causing the material to become more magnetic. To study this, we carried out crystal growth experiments using the molten metal flux method to produce Yb(Bi_1−𝑥 Sb_𝑥 )2 for 𝑥 = 0, 0.25, 0.50, 0.75 & 1. We examined the crystals produced by these experiments using powder x-ray diffraction to assess their crystal structures and magnetic susceptibility to assess the emergence of Curie-Weiss behavior. These measurements show that Bi → Sb substitution results in lattice compression and a trend towards more magnetic behavior, as expected from the Doniach picture.