Induced-Moment Ferromagnetism inPr3Tl

Abstract

It is shown that the intermetallic compound ${\mathrm{Pr}}_3$ Tl is a case of an induced-moment ferromagnet in which the nonmagnetic singlet ground state of ${\mathrm{Pr}}^{3+}$ is spontaneously polarized below 11 °K due to slightly overcritical exchange interactions. By substituting only 7 at.% of La for Pr, both the ordered moment $m_0$ (at 0 °K) and the Curie temperature $T_C$ are reduced to zero, in contrast to the usual behavior of local-moment systems. The observed ratios of $\frac{m_0}{T_C}$ for different La concentrations are compared with theoretical expectations. Specific-heat and resistivity anomalies at the transition are shown to be much reduced from what one would expect in an ordinary ferromagnet.