HIGH-PRESSURE EFFECT ON THE MAGNETIC TRANSITION IN HEAVY-FERMION SYSTEMS CEPD2AL3 AND CEPDAL

We have investigated the pressure dependence of the antiferromagnetic transition temperatures T-N for CePd2Al3 and CePdAl. Although the T-N of both compounds are almost equal at ambient pressure, the pressure d ependences are different; T-N of CePd2Al3 initially increases at a rat e of 0.3 K/GPa, then passes through a maximum near 0.75 GPa and falls rapidly at higher pressures while T-N of CePdAl is pressure insensitiv e in the low pressure region and decreases monotonically in the high p ressure region. The results are discussed in terms of the competition between the Kondo effect and the RKKY interaction and it is shown that the results can be understood by the phase diagram proposed by Doniac h.