Angular Harmonic Hall Voltage and Magnetoresistance Measurements of Pt/FeCoB and Pt-Ti/FeCoB Bilayers for Spin Hall Conductivity Determination

• Published in: IEEE transactions on electron devices Vol. 68; no. 12; pp. 6379 - 6385
• Main Authors: Skowronski, Witold, Grochot, Krzysztof, Rzeszut, Piotr, Lazarski, Stanislaw, Gajoch, Grzegorz, Worek, Cezary, Kanak, Jaroslaw, Stobiecki, Tomasz, Langer, Jurgen, Ocker, Berthold, Vafaee, Mehran
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Anisotropic magnetoresistance (AMR); Damping; Electric potential; Electrical resistance measurement; Electrical resistivity; Electron spin; Electronic devices; ferromagnetic resonance (FMR); Ferromagnetism; Harmonic analysis; Heavy metals; Magnetic multilayers; magnetic thin films; Magnetization; Magnetomechanical effects; Magnetoresistance; Magnetoresistivity; Nonhomogeneous media; Perpendicular magnetic anisotropy; spin Hall effect; spin Hall magnetoresistance (SMR); Spin-orbit interactions; Spintronics; Titanium; Voltage; Voltage measurement
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2021.3122999

Materials with significant spin-orbit coupling enable efficient spin-to-charge interconversion, which can be utilized in novel spin electronic devices. A number of elements, mainly heavy metals (HMs), have been identified to produce a sizable spin current (<inline-formula> <tex-math notation="LaTeX">{j}_{s} </tex-math></inline-formula>), while supplied with a charge current (<inline-formula> <tex-math notation="LaTeX">{j} </tex-math></inline-formula>), detected mainly in the neighboring ferromagnetic (FM) layer. Apart from the spin Hall angle <inline-formula> <tex-math notation="LaTeX">\theta _{\text {SH}}\,\,= {j}_{s}/{j} </tex-math></inline-formula>, spin Hall conductivity (<inline-formula> <tex-math notation="LaTeX">\sigma _{\text {SH}} </tex-math></inline-formula>) is an important parameter, which takes also the resistivity of the material into account. In this work, we present a measurement protocol of the HM/FM bilayers, which enables for a precise <inline-formula> <tex-math notation="LaTeX">\sigma _{\text {SH}} </tex-math></inline-formula> determination. Static transport measurements, including resistivity and magnetization measurements, are accompanied by the angular harmonic Hall voltage analysis in a dedicated low-noise rotating probe station. Dynamic characterization includes effective magnetization and magnetization damping measurement, which enable HM/FM interface absorption calculation. We validate the measurement protocol in Pt and Pt-Ti underlayers in contact with FeCoB and present <inline-formula> <tex-math notation="LaTeX">\sigma _{\text {SH}} </tex-math></inline-formula> of up to <inline-formula> <tex-math notation="LaTeX">{3.3}\,\times \,{10}^{{5}} </tex-math></inline-formula> S/m, which exceeds the values typically measured in other HM, such as W or Ta.