Spin-to-charge conversion efficiency in the topological insulator B i2 T e3 and heavy metals W and Pt stacked with the ferromagnetic Weyl semimetal C o2MnGa

Journal article, 2024

The Weyl semimetal Co2MnGa (CMG) has recently attracted significant attention in the field of condensed matter physics because of its unique topological features along with the simultaneous presence of ferromagnetism at room temperature. Utilizing these remarkable properties of CMG for the spintronic applications will be of great interest both from fundamental as well as technological viewpoints. However, the investigation of spin pumping by means of the inverse spin Hall effect (ISHE) is not yet explored in this material. Here, we report the spin generation, spin propagation, and detection of the efficiency of spin-to-charge conversion (SCC) from CMG to different nonmagnetic (NM) layers such as heavy metals like Pt and W and topological materials like Bi2Te3 through ISHE. The ferromagnetic resonance analyses clearly revealed the dependence of spin relaxation on the spin-orbit coupling strength of the nonmagnets and the concerned interface quality. A large spin mixing conductance of ∼1.8×1019m-2 is observed for W and a quite high value of spin Hall angle of ∼1.5 is evidenced for Bi2Te3 in these CMG based heterostructures. Importantly, a correlation is also established between the interfacial spin transport efficiency and the SCC efficiency with the quality of the NM layer as well as the associated interface. The findings obtained are fortified by the longitudinal spin Seebeck effect (LSSE) measurements. The anomalous Nernst contribution is separated from the spin Seebeck contribution by employing measurements in both in-plane magnetized and out-of-plane magnetized configurations. The anomalous Nernst coefficient for a 20-nm polycrystalline CMG film is found to be independent of measurement geometry with a value estimated to be 0.41 μV/K. The results of the LSSE are coherent with the ISHE measurements obtained for different CMG/NM bilayers. This detailed analysis is fundamentally very vital regarding the underlying principles of spin transport and SCC, and is expected to provide key insights for the strategic fabrication and optimization of spintronic devices.