Pressure effect on valence fluctuation and magnetic ordering in YbPd

The cubic CsCl type compound YbPd is known to be a valence fluctuating compound and to undergo four phase transitions at 0.5, 1.9, 105 and 125 K. In the present study, we focus on pressure effect on the transitions. The transitions at T₁ = 105 K and T₂ = 125 K, which are accompanied by thermal hysteresis, are of first order. With increasing pressure, the transitions shift toward lower temperature direction. The transition at T₁ satisfies the Clausius-Clapeyron's relation, which also supports the first-order transition. T₁ disappears at around 1.5 GPa. Above 1.5 GPa, some new ground state would be realized. We can observe an anomaly at 2.8 K which would be associated with magnetic ordering at 1.9 K. The anomaly becomes more distinct with pressure. Since applying pressure stabilizes magnetic Yb^{3 +}, the magnetic ordering becomes more conspicuous.