Quantifying power flow processes mediated by spin currents

• Published in: arXiv.org 2020-11
• Main Authors: Nakahashi, Kenta, Takaishi, Kohei, Suzuki, Takayuki, Kanemoto, Katsuichi
• Format: Article
• Language: English
• Subjects: Efficiency; Electric potential; Electromotive forces; Energy dissipation; Evaluation; Ferromagnetic resonance; Ferromagnetism; Free energy; Hall effect; Microwave absorption; Photovoltaic cells; Power flow; Propagation; Pumping; Solar cells; Spintronics
• ISSN: 2331-8422

Energy propagation through spin currents has been expected to be one of the most promising ways to achieve dissipation-free energy propagation, but the power flow via spin currents has been unclear as to the efficiency of the power flow and where the power losses occur. Here, we comprehensively evaluate the spin current-mediated power flow process in the bilayer device consisting of ferromagnetic metal (FM) and non-magnetic metal (NM) layers by realizing experimental evaluations for each process from the microwave absorption to electromotive force (EMF) output. The absorption power by ferromagnetic resonance (FMR) of the thin FM layer during the EMF output is directly measured in operando using an antenna probe system. The transfer efficiency of the absorption power into the NM layer by spin pumping is estimated from strict linewidth evaluation of EMF spectra. The maximum transfer efficiency of the spin pumping power to the external load via the inverse spin Hall effect is determined to be 4.2*10-8 under 160mW microwave irradiation using an analysis model similar to that for solar cells. The main factors reducing the efficiency are found to be low resistivity of the NM layer and the interface loss. These findings enhance the applicability of spin current devices and contribute to the development of spin-based technologies.