Properties of Nonstoichiometric SrRu$_{1-v}$O$_{3}$\\Perovskites

Annealing of stoichiometric SrRuO$_{3}$ perovskites in high-pressure oxygen of 600 atm. near 1100$^{\circ}$C produces SrRu$_{1-v}$O$_{3}$ compounds with vacancies on the Ru-sites. The creation of Ru vacancies rapidly suppresses the ferromagnetic ordering temperature, $T_{C}$, from 163 K to 45 K with increase of v $\approx $ 0.09. The resistivity shows a metallic behavior near room temperature with progressively more insulating behavior at low temperatures for increasing v. All samples display clear metallic-like decrease of the resistivity and negative magneto-resistance right below $T_{C}$. Structural changes that accompany creation of Ru-site vacancies indicate reduced charge screening caused by the Ru-vacancies that offsets expected decrease of the average interatomic distance Ru--O. The $b$ and $c$ lattice parameters and the unit cell volume are virtually temperature independent for the stoichiometric material below $T_{c}$. We show that this previously reported invar-effect originates from freezing of the octahedral tilting about the [001] axis that can be observed for both stoichiometric and Ru-deficient samples. Spontaneous magnetostriction has the largest effect on the $b$ axis of the orthorhombic \textit{Pbnm} crystal structure.