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We show that annealing of stoichiometric SrRuO 3 perovskites in high-pressure oxygen of 600 atm near 1100°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 an increase of v Ϸ 0.09. Subtle structural changes that accompany the creation of Ru-site vacancies are different from the typical properties of transition metal perovskites, for which an increased formal oxidation state of the B-site cations normally leads to decreased B-O interatomic distances and contraction of the unit cell volume. The reduced charge screening caused by the Ru-vacancies offsets an expected decrease of the average interatomic distance Ru-O and rotation of the RuO 6 octahedra as Sr atoms relax toward Ru-vacancies increases the observed volume.

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