Intrinsic physics in magnetic Weyl semimetal SrRuO3 films addressed by machine-learning-assisted molecular beam epitaxy

Abstract The itinerant 4 d ferromagnetic perovskite SrRuO 3 [bulk Curie temperature ( T C ) = 165 K] has been studied extensively for many decades because of the unique nature of its ferromagnetism, metallicity, chemical stability, and compatibility with other perovskite-structured oxides. Recently, SrRuO 3 has been gathering renewed interest as a magnetic Weyl semimetal and a two-dimensional ferromagnetic system. Ultra-high-quality SrRuO 3 film growth techniques, combining oxide molecular beam epitaxy technology and a statistical machine learning method, have revealed new physics and physical properties of SrRuO 3 as a magnetic Weyl semimetal, such as quantum transport of Weyl fermions and high-mobility two-dimensional carriers from surface Fermi arcs. This review summarizes the methods of growing ultra-high-quality SrRuO 3 films and the novel physics found in them. In addition, progress in crystal structure analyses and the electrical and magnetic properties of SrRuO 3 over the last decade will also be discussed.