Adsorption-Controlled Growth and Magnetism in Epitaxial SrRuO₃ Films

Controlling defect densities in SrRuO₃ films is the cornerstone for probing the intricate relationship among its structural, electrical, and magnetic properties. We combine film growth, electrical transport, and magnetometry to demonstrate the adsorption-controlled growth of phase-pure, epitaxial, and stoichiometric SrRuO₃ films on SrTiO₃ (001) substrates using solid source metal-organic molecular beam epitaxy. Across the growth window, we show that the anomalous Hall curves arise from two distinct magnetic domains. Domains with similar anomalous Hall polarities generate the stepped feature observed within the growth window, and those with opposite polarities produce the hump-like feature present exclusively in the highly Ru-poor film. We achieve a residual resistivity ratio (RRR = ρ_300K/ρ_2K) of 87 in a 50 nm-thick, coherently strained, and stoichiometric SrRuO₃ film, the highest reported value to date on SrTiO₃ (001) substrates. We hypothesize further improvements in the RRR through strain engineering to control the tetragonal-to-orthorhombic phase transformation and the domain structure of SrRuO₃ films.