Spin-orbitronics in epitaxial CuMnSb/NiMnSb half-Heusler heterostructures

• Applicant: Dr. Johannes Kleinlein
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397861849

In this project spin-orbit torque (SOT) related effects in heterostructures comprised of the half-Heusler alloys CuMnSb (antiferromagnetic, AFM) and NiMnSb (ferromagnetic, FM) will be investigated. Such spin-orbit torques originate from charge currents that get spin polarized when passing through materials with strong spin-orbit coupling (SOC). For ferromagnetic or antiferromagnetic SOC materials, this spin polarization interacts locally with the magnetic moments. This field of experiments that takes advantage ofthe spin-orbit torque is recently called “spin-orbitronics”.As a first step a molecular beam epitaxy growth process for high crystal quality CuMnSb will be further developed and optimized. Single layers of CuMnSb will be grown on InAs (001) substrates; heterostructures of CuMnSb combined with NiMnSb will be grown on InP (001) substrates. As grown samples will be mainly characterized by X-Ray diffraction for crystal properties and quality, as well as by SQUID to determine magnetic parameters. In NiMnSb/CuMnSb heterostructures, the exchange coupling between the FM and the AFM will be of special interest. For electrical characterization a standard hall-bar geometry will be patterned using optical lithography. Here, we material parameters will be determined, such as resistivity or Hall-constant. Several experiments that make use of the spin-orbit torque will be conducted: 1) Single layers of epitaxial CuMnSb will be used to demonstrate switching of the magnetic sublattice of the AFM. Via the anisotropic magnetoresistance (AMR), we will be able to probe the orientation of the magneticsublattice. 2) In a second set of devices, we will combine AFM CuMnSb and ferromagnetic films deposited by sputtering. Here, our main goal is to switch the magnetization of the FM using the spin-orbit torque created in the AFM and the exchange coupling. 3) For the final devices, fully epitaxial NiMnSb/CuMnSb heterostructures will be used to fabricate tunneling anisotropic magnetoresistance devices. These devicesoffer the possibility to investigate magnetic characteristics of the CuMnSb in a magnetotransport experiment by making use of the exchange spring effect.

• DFG Programme: Research Grants