Spintronics relies on magnetization switching through current-induced spin torques. However, because spin transfer torque for ferromagnets is a surface torque, a large switching current is required for a thick, thermally stable ferromagnetic cell, and this remains a fundamental obstacle for high-density non-volatile applications with ferromagnets. Here, we report a long spin coherence length and associated bulk-like torque characteristics in an antiferromagnetically coupled ferrimagnetic multilayer. We find that a transverse spin current can pass through >10-nm-thick ferrimagnetic Co/Tb multilayers, whereas it is entirely absorbed by a 1-nm-thick ferromagnetic Co/Ni multilayer. We also find that the switching efficiency of Co/Tb multilayers partially reflects a bulk-like torque characteristic, as it increases with ferrimagnet thickness up to 8 nm and then decreases, in clear contrast to the 1/thickness dependence of ferromagnetic Co/Ni multilayers. Our results on antiferromagnetically coupled systems will invigorate research towards the development of energy-efficient spintronics.

自旋电子学依靠通过电流感应的自旋转矩进行磁化切换。但是，由于铁磁体的自旋传递转矩是表面转矩，因此对于厚的，热稳定的铁磁电池需要大的开关电流，这仍然是铁磁体的高密度非易失性应用的基本障碍。在这里，我们报告了反铁磁耦合的亚铁磁多层中较长的自旋相干长度和相关的块状转矩特性。我们发现，横向自旋电流可以通过> 10 nm厚的铁磁Co / Tb多层，而它完全被1 nm厚的铁磁Co / Ni多层吸收。我们还发现，Co / Tb多层薄膜的转换效率部分反映了类似体积的转矩特性，与铁磁性Co / Ni多层膜的1 /厚度依赖性形成鲜明对比的是，当铁磁性膜厚度达到8 nm时，它会随着厚度的增加而增加，然后减小。我们在反铁磁耦合系统方面的研究成果将为开发节能型自旋电子器件带来积极的推动。