Challenges in electrical detection of spin-orbit torque in Ir₂₀Mn₈₀/Pt hetero-structures

Issue title: Spintronics: Fundamental and Applications

Guest editors: Mario Carpentieri

Article type: Research Article

Authors: Goksal, Ilkin^a; | Piskin, Hasan^a | Kocaman, Bayram^{a; b} | Akın, Kutay^a | Cay, Dogukan^c | Selvi, Ege^a | Karakas, Vedat^a | Lendinez, Sergi^d | Saglam, Hilal^e | Li, Yi^d | Pearson, John E.^d | Divan, Ralu^f | Zhang, Wei^g | Novosad, Valentine^d | Hoffmann, Axel^h | Ozatay, Ozhan^a

Affiliations: [a] Department of Physics, Bogazici University, Istanbul, Turkey | [b] Department of Electrical & Electronics Engineering, Siirt University, Siirt, Turkey | [c] Department of Electrical Engineering, Istanbul Technical University, Istanbul, Turkey | [d] Materials Science Division, Argonne National Laboratory, Lemont, IL, USA | [e] Department of Electrical Engineering, Princeton University, NJ, USA | [f] Center For Nanoscale Materials, Argonne National Laboratory, Lemont, IL, USA | [g] Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA | [h] Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Correspondence: [*] Corresponding author: Ilkin Goksal,  Department of Physics, Bogazici University, 34470, Istanbul, Turkey. Tel.: +90 5387459821; E-mail: [email protected]. ORCID: https://orcid.org/0000-0002-2827-3276

Abstract: Manipulation of antiferromagnetic sublattice orientations, a key challenge in spintronic device applications, requires unconventional methods such as current induced torques including Spin Transfer Torque (STT) and Spin-Orbit Torque (SOT). In order to observe the deviation of the Néel vector from the anisotropy axis, one of the simplest approaches is the electrical detection, whereby one monitors the change in resistance as a function of applied current. In this work, we have investigated the conditions under which an ultra-thin metallic antiferromagnet, Ir20Mn80 becomes susceptible to SOT effects by studying antiferromagnetic layer structure and thickness dependence in antiferromagnetic metal (Ir20Mn80)/heavy metal (Pt) superlattices. Our electrical measurements reveal that in bilayer structures there exists a shallow range of Ir20Mn80 thicknesses (∼1–2 nm) for which SOT driven control of spins is apparent, whereas for lower thicknesses incomplete sublattice formation and for higher thicknesses improved thermal stability prohibits vulnerability to spin currents. Furthermore, in multilayers, structural changes in Ir20Mn80 layer quenches local torques due to stronger (111) magnetocrystalline anisotropy. These results suggest that an exhaustive optimization of the antiferromagnet parameters is crucial for the successful deployment of spintronic devices.

Keywords: Antiferromagnets, spin Hall effect, VNA-FMR, electronic transport

DOI: 10.3233/JAE-220298

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 73, no. 1, pp. 3-13, 2023