Has CeAl3 a singlet ground state at T = O and is it magnetically ordered between 2.5 and 6K

The competition between the RKKY interactions and Kondo effect in cerium atoms plays an important role in the interpretation of the magnetic properties of CeAl3. The presence of two peaks in the specific heat at 2.5 and 6 K and the occurrence of magnetic ordering demonstrated by the abrupt appearance of a spontaneous magnetization below 6 K have been confirmed. These properties apparently contradict the high linear term in the specific heat γ = 1620 mJ mol-1 which has to be interpreted as being due to the formation of a singlet Kondo ground state at T = O. Simple entropy considerations lead to a Kondo temperature of the order of 3 K. This contradiction can be suppressed be assuming the disappearance of the magnetic ordering at some temperature between 0 and 6 K. The measurements show that the spontaneous magnetization which appears below 6 K decreased abruptly below 2.5 K, confirming the interpretation suggested above. Specific-heat and magnetization measurements under pressure can also be interpreted in that way. It is believed that CeAl3 could be the first example of a metal having a singlet Kondo ground state at T = O, which is however magnetically ordered over a definite range of temperatures T1-T2 confirming the results of other workers. (author)