Interfacial modulation of magnetic relaxation and electrical characteristic in RuO2/CrO2 antiferromagnet-half metal bilayer

Half-metallic chromium dioxide (CrO2) is a promising candidate in magnetic random-access memory (MRAM) devices due to its nearly full spin polarization and ultralow Gilbert damping at room temperature. In this study, we succeeded in fabricating (1 1 0) and (1 0 0)-oriented RuO2/CrO2 bilayers with different thicknesses of CrO2 film using two-step method. The CrO2 film epitaxially grown on a RuO2 layer exhibits a perfect in-plane magnetic uniaxial anisotropy. The magnetic relaxation of CrO2 films can be strongly modulated via the proximity to RuO2 layer, which may relate to the enhancement of the two-magnon scattering due to effects of antiferromagnetic order in RuO2 film. In addition, electronic transport measurements indicate that the electronic characteristic is strongly related to the film growth orientation, and a linear magnetoresistance is observed stemming from intergrain tunneling magnetoresistance and double-exchange mechanism. Angle-dependent ferromagnetic resonance measurements indicates that the uniaxial anisotropy in CrO2 film is strongly related to the strain effect, which is consistent with reciprocal space mapping results. This work lays a foundation for current-drive MRAM based on RuO2/CrO2 bilayer and provides a feasible damping modulation method for CrO2 film.