Abstract
The perovskite ruthenates (ARuO3, A=Ca, Ba, or Sr) exhibit unique properties owing to a subtle interplay of crystal structure and electronic-spin degrees of freedom. Here, we demonstrate an intriguing continuous tuning of crystal symmetry from orthorhombic to tetragonal (no octahedral rotations) phases in epitaxial SrRuO3 achieved via Ba substitution (Sr1−xBaxRuO3 with 0≤x≤0.7). An initial Ba substitution to SrRuO3 not only changes the ferromagnetic properties, but also tunes the perpendicular magnetic anisotropy via flattening the Ru–O–Ru bond angle (to 180∘), resulting in the maximum Curie temperature and an extinction of RuO6 rotational distortions at x≈0.20. For x≤0.2, the reduction of RuO6 octahedral rotational distortion dominantly enhances the ferromagnetism in the system, though competing with the effect of the RuO6 tetragonal distortion. Further increasing Ba substitution (x>0.2) gradually enhances the tetragonal-type distortion, resulting in the tuning of Ru−4d orbital occupancy and suppression of ferromagnetism. Our results demonstrate that isovalent substitution of the A−site cations significantly and controllably impacts both electronic and magnetic properties of perovskite oxides.
