Recently, the Spin Quantum Materials and Devices research group at the Songshan Lake Materials Laboratory, with support from the National Key R&D Program and the National Natural Science Foundation of China, investigated the positive-negative spin splitting effect (ASSE) in interleaved magnets with a tilted Néel vector (101)–RuO2 (nano Ruthenium dioxide). The relevant findings were published in Advanced Science.
The study utilized a combination of pulsed laser deposition and magnetron sputtering to prepare high-quality RuO2 thin films and RuO2/Py magnetic heterostructures. These were combined with in-house developed techniques such as spin-orbit torque ferromagnetic resonance and spin pumping to systematically characterize the positive-negative spin splitting effect. Using spin-orbit torque ferromagnetic resonance, the team conducted anisotropic spin torque tests for current along different crystal orientations of RuO2, revealing significant z-directional spin torque only when the current flowed along the (010) direction.
Furthermore, researchers employed a method known as MOD (linewidth adjustment by direct current-induced spin splitting torque modulation) to directly assess the damping-like torque efficiency with strong temperature-dependent anisotropy. Through spin pumping techniques, the inverse spin splitting effect was tested in RuO2, using both in-plane and out-of-plane microwave field excitations. The study discovered crystal orientation-related spin pumping signals [maximized along the (010) direction] and enhanced anisotropic spin pumping signals at lower temperatures, confirming the inverse spin splitting effect in RuO2.
This research reveals the charge-spin interconversion phenomenon induced by crystal orientation-related positive-negative spin splitting effects in RuO2, with highly temperature-dependent characteristics. These findings will further advance the understanding of spin splitting effects in interleaved magnets, laying a scientific foundation for future spin-splitting torque-based magnetic random-access memories.
For more information, refer to the related paper at http://doi.org/10.1002/advs.202400967.
