Magnetic‐Field Dependent Néel Vector Perturbation and Its Magneto‐Transport Properties of RuO ₂ Epitaxial Films

Abstract (RuO 2 , a prototypical altermagnetic material, has attracted considerable interest in recent years. However, there is still experimental controversy over the antiferromagnetic order of RuO 2 , and little is known about its Néel vector orientation and its dynamic behavior in an external magnetic field. Here, based on the experimental results of magnetoresistance (MR) and anisotropic MR properties of RuO 2 films, the theoretical analysis reveals that the Néel vector deviates from the [001] direction, instead rotating within the (−110) plane at an angle of 26.1° with respect to the z ‐axis of the RuO 2 . Meanwhile, the magnetic moment of Ru atoms is slightly perturbed around the direction of the Néel vector at 9 T, with a maximum perturbation angle along (−110) in‐plane and out‐of‐plane directions of ≈0.47°±0.02° and 0.57°±0.05°, respectively. The anisotropic exchange stiffness constants of the RuO 2 film are calculated for the first time. Furthermore, through spin Hall MR measurements in RuO 2 (110)/Pt bilayer, clear Néel‐vector‐related saturation‐like behavior and sharp angular transitions are observed. The interfacial spin‐mixing conductance at the RuO 2 (110)/Pt bilayers is estimated to be 2.41 × 10 16 m −2 . This study provides experimental evidence for the magnetic ordering in RuO 2 films and elucidates the dynamics of its Néel vector under high magnetic fields).