Spin current from chiral magnons in artificial ferrimagnet.

In condensed matter physics, chirality of elementary particles and quasiparticles plays an important role in many unconventional phenomena such as the quantum Hall effect and the chiral phonon excitations . In magnetic materials, magnons are chiral quasiparticles to characterize the quantized spin excitations. However, chiral phenomena of magnons have been barely studied because magnons in ferromagnets (FM) carry right-handed chirality only. Although antiferromagnets (AFM) support both right-handed and left-handed chiralities of magnons , , chiral phenomena induced by AFM magnons remain unspecified to date because of the complex in spin dynamics , and the obstacles of THz broadband magnetic excitations , . On the contrary, ferrimagnets, which combine the characteristics of FM and AFM, offer a new opportunity for the exploration of chiral phenomena in GHz frequency range , . Here we report chiral spin pumping in artificial ferrimagnet of Py/Gd/Py/Gd/Py/Pt multilayers. We realized both right-handed and left-handed chiralities of the Py magnetization precessions at high and low temperature, respectively, and demonstrate unambiguously that opposite chiralities of Py precession pump opposite spin polarizations of the spin current into the Pt layer. Our result promises new functionalities and computing architectures in spintronics based on the chirality of magnons.