12. W. J. Kong, Y. R. Ji, X. Zhang, H. Wu, Q. T. Zhang, Z. H. Yuan, C. H. Wan, X. F. Han, T. Yu, K. Fukuda, H. Naganuma and M. Tung, Field-free spin Hall effect driven magnetization switching in Pd/Co/IrMn exchange coupling system, Appl. Phys. Lett. 109, 132402 (2016)