Mapping microwave field distributions via the spin Hall effect

Abstract

The spatial variation of the spin pumping–inverse spin Hall effect was studied in a palladium/permalloy bilayer via a coplanar waveguide ferromagnetic resonance (CPW-FMR) broadband technique. The inverse spin Hall signal is both inhomogeneous and asymmetric with respect to both the position along the CPW and the excitation port. Based on this observation, we show how the inverse spin Hall effect can be used as a sensitive probe for mapping the microwave magnetic field distribution in the FMR frequency range.

Dependence of spin-pumping spin Hall effect measurements on layer thicknesses and stacking order

“…2, the precession angle θ can be directly estimated from the AMR voltage contribution assuming that the precession angle is uniform along the whole length and that the correlation between the rf field hrf from the CPW and the microwave current flowing in the bilayer is well established. However, it was recently shown that these assumptions do not hold [26], and, as will be shown, these assumptions can lead to large discrepancies in the estimates of the spin Hall angles when reversing the bilayer stacking order. In the limit of small precession angle θ =hrf cos(α)/ΔH (ΔH being the half linewidth at half !"…”

“…5(c), indicates that the SiO2/15Pd/15Py sample has a minimum microwave transmission at 8 GHz, whereas the power transmission remains fairly constant between 7 and 10 GHz for the SiO2/15Py/15Pd sample. This different behavior may reflect differences of impedance mismatch for different samples, which may result in varying standing--wave patterns for the microwaves in the samples [26]. Considering possible spatial inhomogeneities of the microwave field along the sample, calibrating the cone angle with the AMR--FMR method has the advantage that its dependence on the cone angle is identical to that obtained from the SHE voltage (see Eq.…”

“…The issue of phase mixing is complex, as it appears to vary drastically with the sample geometry and frequency. Additional complications may arise from a non--uniformity of the microwave power along a coplanar waveguide [26], which can lead to systematic error in the analysis of the lineshape. Therefore, the choice of a suitable geometry that addresses the effect of interest is crucial.…”

Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

“…This geometry minimizes inductively coupled currents 27 that complicate the analysis of SHE measurements based on spin pumping. 14,15,28,29 Py(20 nm)/Pt(t Pt nm) bilayers (where the Pt thickness ranges from 0-10 nm) in the shape of a 20-lm  2-mm stripe were deposited on Si substrates with 300-nm-thick thermally grown SiO 2 . Four electrical leads for the electrically detected ferromagnetic resonance (FMR) are connected to the bilayer before integration with the coplanar wave-guide (CPW).…”

Temperature and microwave near field imaging by thermo-elastic optical indicator microscopy

“…Various approaches have been proposed based on different kinds of physical phenomena45678910111213. They often rely on scanning probe techniques with carefully designed scanning probes, particular materials and physical processes.…”