Braun, E., A. BÃ¼rger, G. L. Nieva, B. Roden, and J. G. Sereni. "Unexpected magnetic behaviour in a singlet crystal field ground state induced by Tb 4f-instability." Zeitschrift fÃ¼r Physik B Condensed Matter 70, no. 2 (1988): 187–192.
Abstract: The magnetic susceptibility (chi) of Th1-x Tb x alloys (with 5<x<55a/o Tb) in the range of 1 K<T<350K and the specific heat (forx=1.5a/o Tb) for 0.5<T<10 K were measured. A maximum in chi(T) was observed at a temperature which depends on concentration. The crystal field level scheme that fits the specific heat measurements shows two non-magnetic singlets as lowest levels. Such ambiguity is discussed within the framework of the 4f-Tb instability. The results are in agreement with the matrix superconductiveT c decrease. The contribution of the interconfigurational mixing on chi and the specific heat is also discussed.