Low-temperature thermal and high-pressure studies of CePd and CeAgSb2

The anomalous properties of the Kondo lattice CeAgSb2 are compared with the well behaved Kondo system, CePd. The low-temperature thermal expansion of CePd is in agreement with previous heat capacity data, showing a ferromagnetic transition at Tc=6.5 K and a second transition at 3.5 K probably due to reorientation of the magnetic moments. The Grueneisen factor, calculated from thermal-expansion and heat capacity is γG∼4.5, the same as the Grueneisen factor γP calculated from the pressure dependence and comparable to a previous measurement of γP approx. 6. Thermal expansion measurements (in fields of up to 8 T) and ac susceptibility measurements (under pressures of up to 7.33 kbar) have been made on CeAgSb2 in the temperature range 1.6-40 K. The zero-pressure ac susceptibility measurements confirm that there is an antiferromagnetic transition at TN=9.5 K, as previously reported. The magnetic contribution to the linear thermal-expansion coefficient of polycrystalline CeAgSb2 (αp) in zero magnetic field has a maximum value near 17 K and becomes small by 29 K. There is no peak in αp at the Neel temperature. The Neel temperature is found to decrease under pressure at the rate of ∂(ln TN)/∂P=-10.1 Mbar-1, which indicates that CeAgSb2 is a magnetic Kondo lattice (with TK>TN) on the right-hand side of the Doniach diagram. (author)