Quantifying Spin-Charge Conversion Mechanisms for THz Emission in Magnetic Multilayers

Ultrafast control of both electric and spin currents triggered by femtosecond laser pulse has attracted much attention due to future applications for broadband THz emitter as well as high-speed spintronic devices. Optically generated spin current is converted to charge current via multiple spin-charge conversion mechanisms, generating THz wave emission in magnetic multilayers. However, to date, quantitative and comparative investigation of THz emission originating from spin-charge conversion mechanisms has not yet been fully explored. Here, direct and straightforward nondestructive probing to measure THz emission is provided at original Co/Pt and Co/Ta interfaces embedded in Pt/Co/Ta multilayers with polarization analysis of both optical pump and THz emission. These results allow a fundamental understanding of various spin-charge conversion phenomena, which is a key basis for future spintronic THz source development. The first quantitative approach to separate multiple spin-charge conversion mechanisms in magnetic multilayer is reported. The approach is based on THz-based experiment, which can be nondestructive probe for the THz emission at original interfaces embedded in multilayers. The work provides a quantitative analysis of spin-charge conversion phenomena, which can be a key for developing THz source based on magnetic multilayers. image