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 L$\text{a}$,Gd]B₆ and L$\text{a}$,Dy]B₆ with different concentrations of rare earth ions. The resistance of these alloys varies as $\text{～ T}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ 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.