Observation of localized moments, Kondo effect, spin glass regime, magnetic ordering in rare earth system with unstable valence

The authors have concluded that a non-magnetic compound or a compound near a magnetic instability always contains imperfections which induce localized moments. Low temperature electronic properties will be strongly affected by these accidental defects which depend upon the sample history. The Kondo effect is often observed in metallic phases. Many new results seem to illustrate this point of view. The presence of Sm3+ has been found in many SmS compounds leading to Kondo effect or to spin glass ordering. Tm2+ is also present as Kondo impurities in Tm3+Se and Tm3+S. These last compounds are Kondo compounds when Tm3+ excited levels are populated. They are new examples of Van Vleck compounds giving Kondo effect similar to the effects observed in LaPrSn3. In some compounds such as CeAl3, magnetic interactions compete with the Kondo condensation so that weak antiferromagnetism is superimposed on the usual properties of a system in a singlet Kondo ground state. 62 references