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.