Pressure-induced valance change in Ytterbium intermetallic YbCuGa

Ytterbium (Yb) intermetallic systems are known to exhibit intermediate valence (IV) behavior due to the hybridization of two energetically close localized configurations, the non-magnetic Yb²⁺ (4f¹⁴) and the magnetic Yb³⁺ (4f¹³), with the conduction electrons. The IV behavior plays a crucial role in the exhibition of anomalous properties of several rare-earth compounds. Pressure and temperature variation can tune the valency of these types of compounds and increase in pressure tends to delocalize these systems and they show tendency to move towards trivalent state Yb³⁺ (4f¹³). YbCuGa is one such compound which shows very intriguing electronic properties owing to its IV. Previous experimental work on YbCuGa at ambient pressure showed IV nature of Yb ions. We report on high pressure, 0-14 GPa, x-ray absorption measurements in partial fluorescence yield mode on YbCuGa system at ambient temperature. Increase in pressure delocalizes the system and pushes it from a valency of ~ 2.58 at ambient pressure to ~ 2.9 at 14.0 GPa. Our results indicate that application of pressure pushes the Yb ion to a magnetic state and therefore magnetic interactions can be expected to dominate as the unit cell volume is decreased.