Ferromagnetism in perovskites Sr$_{1-x}$Pb$_{x}$RuO$_{3}$ (0 $\le $ x $\le $ 1)

Orthorhombic SrRuO$_{3}$ is a well-known metallic ferromagnet with T$_{c}$ $\approx $ 165 K.$^{1}$ We have demonstrated that a complete solid solution of the orthorhombic perovskites Sr$_{1-x}$Pb$_{x}$RuO$_{3}$ can be made with high-pressure synthesis. Whereas the ground state for the whole series remains metallic, the Pb substitution reduces the Curie temperature and eventually ferromagnetic phase is totally suppressed at x $\approx $ 0.5. Moreover, an unusual low-temperature phase with the Imma space group is developed through a first-order transition below T$_{t} \quad \approx $ 90 K in the orthorhombic PbRuO$_{3}$. Based on physical properties measurements on a small grain of the high-pressure product PbRuO$_{3}$, we have shown that the transition at T$_{t}$ is a metal-metal transition. T$_{t}$ is suppressed below 10 K under high pressure 3GPa as verified by the structural study with a diamond anvil cell with synchrotron radiation. Suppression of ferromagnetism in this system can be attributed to the hybridization of the Pb$^{2+}$ 6s electrons with the Ru 4d electrons that broadens the Ru 4d band. $^{1}$ G. Cao, et al., Phys. Rev. B \textbf{56}, 321 (1997). $^{2 }$S. A. J. Kimber, et al., Phys. Rev. Lett. \textbf{102}, 046409 (2009). $^{3 }$J.-G. Cheng, et al., Phys. Rev. B, in press.