Spin-glass behaviour of [La,Gd]B6 and [La,Dy]B6 alloys

Electrical resistance and absolute thermoelectric power measurements have been made in the temperature range between 2 and 30 K on a few polycrystalline specimens of [La,Gd]B6 and [La,Dy]B6 with different concentrations of rare earth ions. The resistance of these alloys varies as approximately equal to Tsup(3/2) which is characteristic of spin glasses at low temperature. The thermoelectric power of all specimens but one, shows a broad positive peak in the lower part of the temperature range and becomes negative at higher temperatures, a feature that is typical of a spin glass to paramagnetic phase transition. The exceptional specimen has a large Gd concentration and its thermoelectric power remains positive to higher temperatures than would be expected for a spin glass. (author)