||川﨑 雅司 教授
||Exploration of novel properties in perovskite Ru(III) oxides LnRuO3 stabilized by thin film fabrication
|| Ruthenium oxide has attracted interests because of its itinerant 4d electrons. For example, RuO2 and Sr2RuO4 are superconductors, SrRuO3 is a ferromagnet with Weyl-fermion behavior, *A*-site substitution (Ca2+, Ba2+, Pb2+) of SrRuO3 is also extensively researched to clarify a relationship between the magnetism and RuO6 distortion.
However, although Ru may take from 2+ to 8+, most of the studies are concentrating on Ru(IV) oxides. Here, we focus on perovskite LnRuO3, which contains Ru3+ ion in B-site. Ru3+ has the same t2g5 electron configuration as Rh4+ and Ir4+ in perovskite rhodate ARhO3 and iridate AIrO3. In those t2g5 system, an unusual insulator behavior which origins from J = 1/2 ground state and a Dirac semimetal state was observed in iridates. In Ru(III) perovskite, besides the effect of t2g5 electrons, magnetic moment from Ln3+, which is absent in ARhO3 and AIrO3, may correlate with Ru3+ and therefore influence the magnetic properties. Additionally, a (111) bilayer structure of LaRuO3 on LaAlO3 substrate is theoretically predicted to be a topological metal. From these reasons, the exploration of LnRuO3 series may open a new playground for 4d perovskite materials.
From several previous reports, high pressure (over 10GPa) is needed to synthesize most of polycrystalline bulk LnRuO3 except for LaRuO3, indicating single crystals are challenging to obtain. Therefore, properties of LnRuO3 are still unclear.
In our study, we aim to fabricate single crystalline thin films of LnRuO3 by epitaxial stabilization using pulsed laser deposition and reveal their magnetotransport properties.