2026/07/17 by Yudi Yang, Zhuang Qian, Shi Liu +1
#cond-mat.mtrl-sci
The magnetic ground state of the altermagnet candidate RuO2 remains controversial, with magnetic signatures observed mainly in epitaxial films. Here we show, using first-principles calculations, that magnetism in epitaxial RuO2 can emerge as an interfacial boundary phase at TiO2/RuO2 interfaces. While TiO2-induced epitaxial strain alone does not make (001)-oriented RuO2 magnetic, explicit TiO2/RuO2 interfaces stabilize sizable Ru moments confined to the first few Ru layers. Charge-density and orbital-resolved analyses reveal interfacial electronic reconstruction, and substrate doping provides a route to tune the induced moments. In symmetric TiO2/RuO2/TiO2 heterostructures, the two magnetic interfaces couple through the metallic RuO2 spacer, producing a thickness-dependent alternation between weak-ferromagnetic and compensated altermagnetic states. Our results identify interface engineering as a practical route to stabilize and control fragile magnetism in RuO2.