Pressure effects on magnetic susceptibility of intermediate-valence compound YbAl3

Recently, there have been considerable interests in a slow crossover from Fermi liquid behaviour to local moment behaviour for YbAl3. We have investigated the pressure effects on the magnetic susceptibility of single-crystalline YbAl3 as a function of temperature (2-300 K) and hydrostatic pressure (up to 1 GPa). At ambient pressure the susceptibility shows a broad maximum of chi(max) at T-max similar to 116 K, consistent with a high Kondo temperature T-K similar to 500 K. Below coherent temperature T-coh similar to 40 K, the susceptibility shows anomalous enhancement with a small maximum at T-mL similar to 17 K, and reaches constant value of chi(0) below 5 K. The application of pressure causes an increase in the susceptibility over the entire temperature range. Both the characteristic temperatures T-max and T-mL decrease with increasing pressure. We find that above T-coh the temperature and pressure dependence of chi/chi(max) obey a universal curve scaled with reduced temperature T/T-max. On the other hand, below T-coh, chi/chi(max) deviates from the universal curve and is increased by applied pressure. The Gruneisen parameter for T-K and T-coh are -2.2 and -4.6 similar to 12, respectively. These results indicate that T-coh/T-K is decreased by applied pressure in YbAl3.