Tuning Structural, Transport and Magnetic Properties of Epitaxial SrRuO3 through Ba-Substitution

TL;DR

This study demonstrates how Ba-substitution in epitaxial SrRuO3 allows continuous tuning of its crystal symmetry, magnetic properties, and electronic structure, revealing the interplay between structural distortions and ferromagnetism in perovskite oxides.

Contribution

It introduces a method to controllably modify the structural, magnetic, and electronic properties of SrRuO3 via Ba-substitution, highlighting the role of octahedral distortions.

Findings

Ba-substitution induces a transition from orthorhombic to tetragonal phases.

Maximum Curie temperature achieved at x=0.20 Ba content.

Suppression of RuO6 rotational distortions enhances ferromagnetism.

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{\deg}), resulting in the maximum Curie temperature and an extinction of RuO6 rotational distortions at x = 0.20. For x > 0.2, the suppression of RuO6 octahedral rotational distortion dominantly enhances the ferromagnetism in the system, though competing with the impact of the RuO6 tetragonal distortion. Further increasing 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.