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

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 (${j}_{s}$), while supplied with a charge current (${j}$), detected mainly in the neighboring ferromagnetic (FM) layer. Apart from the spin Hall angle $\theta _{\text {SH}}\,\,= {j}_{s}/{j}$ , spin Hall conductivity ($\sigma _{\text {SH}}$) 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 $\sigma _{\text {SH}}$ 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 $\sigma _{\text {SH}}$ of up to ${3.3}\,\times \,{10}^{{5}}$ S/m, which exceeds the values typically measured in other HM, such as W or Ta. [ABSTRACT FROM AUTHOR]