Design and time-resolved magneto-optical advanced characterization of Heusler compounds with large Spin-Orbit Coupling

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This project will focus on the interplay of exchange and spin-orbit interaction in advanced, Heusler-based materials. As the energy scale of exchange and spin-orbit interaction in magnetic materials corresponds to the sub-picosecond scale in the time-domain, time-resolved studies with femtosecond resolution are the ultimate tool in order to gain access to the interplay of those two important interactions for spin-relaxation.We will design new Heusler compounds with extremely large spin-orbit coupling, synthesize these compounds, and perform basic characterization. Advanced characterization will be performed by means of time-resolved magneto-optical methods, giving access to the ultrafast demagnetization as well as to the ultrafast magnetization switching in materials with specifically engineered spin orbit coupling as well as perpendicular anisotropy. The knowledge about spin-dependent electron dynamics acquired in such experiments can be easily transferred to interpret more general spintronics phenomena where magnetization is influenced by currents or vice-versa.The project is organized into two subprojects:a) Design of Heusler compounds with large Spin-Orbit Couplingb) Time-resolved magneto-optical characterization of Heusler compounds with large Spin-Orbit CouplingThe goal of the first subproject is the design and investigation of new compounds with extremely large spin-orbit coupling for potential applications in spintronic devices. Large spin-orbit coupling can be expected for Heusler compounds comprising high-Z elements. Especially, Heusler compounds with Sn and/or Bi on the Z-position and Pd, Pt, Ir, Ru, Rh, and Au are potential candidates. Several possible ferro- and ferrimagnetic compounds will be synthesized and investigated within the project such as X2YBi (with X= Pd, Pt, Ir, Ru, Rh, Au and with Y=TM) with cubic as well as Mn2YSn and Mn2YBi (with Y= Pd, Pt, Ir, Ru, Rh, Au) with tetragonal structure. Targets will be provided for the thin films and devices groups. In the last year of the project we will try to design a Heusler compound which is suitable for all-optical switching. This effect has been achieved up to now only in the ferrimagnetic compound GdFeCo. We will try to achieve this goal by using in the first step a Heusler compound with Gd and in the second step to exchange the Gd by Mn to end up in a rare earth free compound for all-optical switching applications.The goal of the second subproject is the advanced characterization. We will study ultrafast magnetization dynamics and the feasibility of ultrafast all-optical switching in the advanced Heusler materials optimized in subproject a). Ultrafast magnetization dynamics will be probed with the time-resolved magneto-optical Kerr effect (TR-MOKE) on specifically designed materials with fixed valence number but tunable spin-orbit coupling. This will allow pinpointing the role of spin-orbit coupling in the ultrafast demagnetization process and provide vital information about the microscopic origin of spin relaxation in advanced Heusler materials. The feasibility of alloptical switching will be tested on specifically designed ferrimagnetic Heusler compounds to verify the feasibility of this process in technologically relevant materials with high perpendicular magnetic anisotropy.