Unusual magnetoresistance (UMR)—a change in resistivity when magnetization rotates perpendicular to the current—has long puzzled researchers. Traditionally linked to spin Hall magnetoresistance (SMR) and other spin-current-based models, UMR has been widely observed even in systems where these mechanisms should not apply. This inconsistency has fueled a proliferation of alternative explanations, from Rashba-Edelstein MR to orbital Hall MR.
Now, a study led by Prof. Lijun Zhu (Institute of Semiconductors, CAS) and Prof. Xiangrong Wang (CUHK) provides experimental evidence that UMR has a far simpler and universal origin: interfacial electron scattering governed jointly by the magnetization vector and interfacial electric field. Dubbed two-vector magnetoresistance, this model reproduces key features of UMR—including giant signals in single-layer magnetic metals, high-order contributions, and a striking universal sum rule—without invoking spin or orbital currents or crystalline symmetry.
Re-examining decades of experimental data, the researchers show that results once attributed to SMR or other specialized MR effects can be consistently and naturally explained within the two-vector MR framework. Their findings not only challenge the long-standing dominance of spin-current-based theories but also establish a unified physical origin for UMR across diverse materials and devices.
The study offers a simpler, universal foundation for understanding magnetoresistance phenomena and their technological applications.