Spin Transport in RuO 2 -Based Antiferromagnetic Tunneling Junctions

Abstract Antiferromagnetic materials have attracted considerable interest for next-generation spintronic applications due to their ultrafast spin dynamics and robustness against magnetic field perturbations. However, their zero net magnetic moment poses fundamental challenges for electrical readout and manipulation. The recent discovery of spin-split antiferromagnets, or altermagnets, offers a promising route to overcome these obstacles by enabling spin-polarized transport even without net magnetization. Here, we investigate the spin-dependent transport properties of $\mathrm{RuO}_2$-based antiferromagnetic tunnel junctions through first-principles quantum transport calculations. Focusing on the ($\bar{1}10$) crystallographic orientation of $\mathrm{RuO}_2$, which supports longitudinal spin-polarized currents, we construct three junction configurations with distinct interfacial structures. Our calculations show that significant spin polarization near the Fermi level can up to 36.15%. Under finite bias, we observe deterministic switching of the spin current direction, with the switching threshold ranging from 320 to 360 mV depending on the interface. Furthermore, thermally driven spin currents exhibit a near-linear dependence on temperature gradients. These findings demonstrate that interfacial engineering in $\mathrm{RuO}_2$-based tunnel junctions enables efficient generation and control of spin currents.