Characterization of Epitaxially Grown RuO₂ Thin Films via Magnetron Sputtering

Antiferromagnetic materials (AFM) have garnered significant attention in the field of spintronics due to their advantageous features, including the absence of stray fields, immunity to external magnetic field perturbations, and ultrafast spin dynamics. As a result, antiferromagnetic spintronics holds great promise for surpassing current technologies in terms of speed, efficiency, and functionality. However, the manipulation of antiferromagnetic order, the Néel vector, poses challenges due to the degeneracy of spin-up and spin-down energy bands. Recently, a class of materials known as altermagnetic materials has emerged, exhibiting momentum-dependent spin-splitting phenomena despite their compensated magnetic moments. This discovery has sparked considerable interest in the scientific community. In this study, we present the successful fabrication of altermagnetic metal RuO₂ using magnetron sputtering. Methods to fabricate different textured RuO₂ films have been developed and in-plane XRD scans demonstrated the epitaxial growth of RuO₂ thin films. The elemental composition and excitation modes of RuO₂ films were verified by x-ray photoelectron spectroscopy (XPS) and Raman scattering measurements respectively. The momentum dependent spin-splitting effect have been verified with spin-torque ferromagnetic resonance (ST-FMR) experiment. Notably extra unconventional z-component of anti-damping torque is observed in (101)-oriented RuO₂ film, while passing current along the [010] direction. Overall, our findings highlight the successful fabrication and characterization of altermagnetic metal RuO₂ thin films, shedding light on their potential for advancing the field of antiferromagnetic spintronics