Pressure effects on magnetic susceptibility of intermediate-valence compound YbAl3

Abstract

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 χmax at Tmax ∼ 116 K, consistent with a high Kondo temperature TK ∼ 500 K. Below coherent temperature Tcoh ∼ 40 K, the susceptibility shows anomalous enhancement with a small maximum at TmL ∼ 17 K, and reaches constant value of χ0 below 5 K. The application of pressure causes an increase in the susceptibility over the entire temperature range. Both the characteristic temperatures Tmax and TmL decrease with increasing pressure. We find that above Tcoh the temperature and pressure dependence of χ/χmax obey a universal curve scaled with reduced temperature T/Tmax. On the other hand, below Tcoh, χ/χmax deviates from the universal curve and is increased by applied pressure. The Grüneisen parameter for TK and Tcoh are -2.2 and -4.6∼12, respectively. These results indicate that Tcoh/TK is decreased by applied pressure in YbAl3. © 2010 IOP Publishing Ltd.