Induced-Moment Systems: Paramagnetic Region ofLa3Tl-Pr3Tl

Abstract

Superconducting and magnetic properties in the ${\mathrm{La}}_3$Tl-${\mathrm{Pr}}_3$Tl system are discussed. Superconductivity persists up to very high Pr concentrations, ${\mathrm{Pr}}^{3+}$ being in a crystal-field-singlet ground state. The Van Vleck susceptibility per ${\mathrm{Pr}}^{3+}$ ion at $T=0\mathrm{}$ increases with increasing Pr concentration, indicating ferromagnetic exchange coupling between the Pr ions. At concentrations higher than 93-at.% Pr the system becomes ferromagnetic. No current theoretical model accounts for the observed magnetic behavior.