Giant Piezomagnetic Effect in RuO2 Arising from C-Paired Spin-Momentum Locking

We research the giant Piezomagnetic (PZM) effect in C-paired spin-splitting antiferromagnetic (AFM) RuO2, which exhibits a novel nonlinear PZM effect when crystal symmetry is broken. We have discovered that even in the linear response regime, the PZM coefficients can exhibit unconventional nonlinear behavior due to the existence of high-order PZM tensors. Using group theory and symmetry analysis, we have derived all non-zero linear and high-order PZM tensors and obtained their values from DFT calculations. These tensors are larger than those of most materials, making the PZM effect easily detectable in experiments and providing potential avenues for novel spintronics. Additionally, we have analytically demonstrated the completeness of strain tensors in predicting the PZM effect under any type of strain.