Kondo Effect in the (Y, Tm)S Dilute System

Abstract

The 4f instability occurring in a large number of rare earth (RE) compounds can also be observed in many dilute RE systems (1,2). In the particular case of thulium, it has been shown (3,4) that the intermediate-valent (IV) character of this ion, which was established in the compound TmSe, subsists in (Y, Tm)Se and (La, Tm) Se solid solutions, even for concentrations below 1 % Tm. Furthermore, Kondo and spin glass-like effects occur in these two systems (5,6). Similarly, it has been shown (7,8) that in an alloy Y1−xTmxS, with x = 0.1, the valence state of Tm is close to 3, as in the Konao-lattice compound TmS. The resistivity of this alloy also contains a Kondo contribution proportional to that observed in TmS. Since then, we have performed more detailed studies on other Y1−xTmxS alloys with nominal compositions x = 0.01, 0.07 and 0.1. The results confirm the previous observations of refs. 7, 8 and provide new interesting informations about the Kondo effect in this system. Here, we limit ourselves to susceptibility, resistivity and magnetoresistance measurements.