Thickness Dependent Itinerant Ferromagnetism in Ultrathin Ba-Doped SrRuO3 films

TL;DR

This study investigates how ultrathin Ba-doped SrRuO3 films exhibit thickness-dependent changes in electronic and magnetic properties, revealing a transition from ferromagnetic metal to non-magnetic insulator as thickness decreases.

Contribution

It demonstrates the impact of film thickness and Ba-doping on the structural, electronic, and magnetic phase transitions in SrRuO3 thin films, highlighting the dominance of dimensional effects over chemical disorder.

Findings

Ba-doping reduces RuO6 distortions and induces tetragonal lattice expansion.

A metal-to-insulator and ferromagnetic to non-magnetic transition occurs below 10 unit cells.

Dimensional confinement effects outweigh chemical disorder in property changes.

Abstract

The electronic and magnetic properties in ABO3 perovskite oxides are extremely sensitive to lattice structure but also the dimensionality, such as the thickness in thin film form. Here, we report the thickness-dependent electro-magnetic properties of ultrathin epitaxially stabilized Sr1-xBaxRuO3 (x = 0.08, 0.2) thin films on SrTiO3 (001) substrate. The results reveal that the Ba-doping (0.08 < x < 0.20) reduces RuO6 orthorhombic distortions existing in SrRuO3 and induces a tetragonal distortion as evidenced by out-of-plane lattice expansion. A metal-to-insulator transition, accompanied by a ferromagnetic to non-magnetic transition occurs with reducing film thickness from 10 to 3 unit-cell (u.c.) for both x = 0.08 and 0.2, regardless of the doping level. The results suggest that the effects of compositional vacancies and surface/interface contributions introduced via dimensional confinement are more dominant than A-site chemical disorder or structural distortion for the loss of metallicity and ferromagnetism in ultra-thin epitaxial films.