Browsing by Author "Elliott, Peter"
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- ItemAb-Initio Real-Time Magnon Dynamics in Ferromagnetic and Ferrimagnetic Systems(Weinheim : Wiley-VCH, 2020) Singh, Nisha; Elliott, Peter; Dewhurst, J. Kay; Gross, E.K.U.Magnonics—an emerging field of physics—is based on the collective excitations of ordered spins called spin waves. These low-energy excitations carry pure spin currents, paving the way for future technological devices working at low energies and on ultrafast timescales. The traditional ab-initio approach to predict these spin-wave energies is based on linear-response time-dependent density functional theory (LR-TDDFT) in the momentum and frequency regime. Herein, the simulation of magnon dynamics using real-time time-dependent density functional theory is demonstrated, thus extending the domain of ab-initio magnonic studies. Unlike LR-TDDFT, this enables us to observe atom-resolved dynamics of individual magnon modes and, using a supercell approach, the dynamics of several magnon modes can be observed simultaneously. The energies of these magnon modes are concurrent with those found using LR-TDDFT. Next, the complex dynamics of the superposition of magnon modes is studied, before finally studying the element-resolved modes in multisublattice magnetic systems.
- ItemOptical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy([London] : Nature Publishing Group UK, 2020) Willems, Felix; von Korff Schmising, Clemens; Strüber, Christian; Schick, Daniel; Engel, Dieter W.; Dewhurst, J. K.; Elliott, Peter; Sharma, Sangeeta; Eisebitt, StefanOptically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate this, we perform a joint theoretical and experimental investigation to determine the transient changes of the helicity dependent absorption in the extreme ultraviolet spectral range. We show that the helicity dependent absorption is directly related to changes of the transient spin-split density of states, allowing us to link the origin of OISTR to the available minority states above the Fermi level. This makes OISTR a general phenomenon in optical manipulation of multi-component magnetic systems.
- ItemTransient spin injection efficiencies at ferromagnet/metal interfaces(Weinheim : Wiley-VCH, 2022-10-19) Elliott, Peter; Eschenlohr, Andrea; Chen, Jinghao; Shallcross, Sam; Bovensiepen, Uwe; Dewhurst, John Kay; Sharma, SangeetaSpin injection across interfaces driven by ultrashort optical pulses on femtosecond timescales constitutes a new way to design spintronics applications. Targeted utilization of this phenomenon requires knowledge of the efficiency of non-equilibrium spin injection. From a quantitative comparison of ab initio time-dependent density functional theory and interface-sensitive, time-resolved non-linear optical experiment, the spin injection efficiency (SIE) at the Co/Cu(001) interface is determined, and its microscopic origin, i.e., the influence of spin-orbit coupling and the interface electronic structure, is discussed. Moreover, we theoretically predict that the SIE at ferromagnetic–metal interfaces can be optimized through laser pulse and materials parameters, namely the fluence, pulse duration, and substrate material.