Disentangling Spin, Anomalous, and Planar Hall Effects in Ferromagnet–Heavy-Metal Nanostructures

Abstract

Ferromagnetic (FM)/heavy metal (HM) nanostructures can be used for the magnetic state readout in the proposed magneto-electric spin-orbit logic by locally injecting a spin-polarized current and measure the spin-to-charge conversion via the spin Hall effect. However, this local configuration is prone to spurious signals. In this work, we address spurious Hall effects that can contaminate the spin Hall signal in these FM/HM T-shaped nanostructures. The most pronounced Hall effects in our Co50Fe50/Pt nanostructures are the planar Hall effect and the anomalous Hall effect generated in the FM nanowire. We find that the planar Hall effect, induced by misalignment between magnetization and current direction in the FM wire, is manifested as a shift in the measured baseline resistance, but does not alter the spin Hall signal. In contrast, the anomalous Hall effect, arising from the charge current distribution within the FM, adds to the spin Hall signal. However, the effect can be made insignificant by minimizing the shunting effect via proper design of the device. We conclude that local spin injection in FM/HM nanostructures is a suitable tool for measuring spin Hall signals and, therefore, a valid method for magnetic state readout in prospective spin-based logic.

Charge-induced artifacts in non-local spin transport measurements: How to prevent spurious voltage signals

“…It is important to note that equations 11 and 12 are no longer valid if the ferromagnetic electrodes exhibit fringe or stray fields that can act on the DUT. Such fields are well known to complicate the analysis of spin measurements [23,[75][76][77][78][79] and can appear in quite different forms: 1.) As long as the width of the electrode is small enough that a single-domain magnetization prevails [42], fringe fields with relevant strengths should only be located at the electrode's two faces that are normal to the electrode's easy-axis [42,80].…”

“…As long as the width of the electrode is small enough that a single-domain magnetization prevails [42], fringe fields with relevant strengths should only be located at the electrode's two faces that are normal to the electrode's easy-axis [42,80]. Stray fields can impact the measurement if these two faces are placed too close to or even on top of the transport channel [23,75,76]. 2.)…”

Quantum oscillations of the nonlinear planar effects signifying chiral anomaly in Weyl Semimetals

“…However, it has been gradually realized that both these two planar magneto transport effects, namely, the positive LMC and PHE, are not sufficient transport signatures to guarantee the presence of CA in WSMs. Recently, it has been reported that similar planar transport behaviors can also arise through various extrinsic mechanisms [11,[15][16][17][18][19] and even appear in * ygyao@bit.edu.cn materials without any Weyl nodes [20][21][22][23][24][25][26][27][28][29][30][31][32]. In addition, Weyl nodes themselves do not always exhibit positive LMC.…”

All-Electrical Spin-to-Charge Conversion in Sputtered BixSe1-x

“…We should mention that an anomalous Hall effect (AHE) ,, and ordinary Hall effect (OHE) can appear as artifacts in the measured SCC signals (Note S3 in the Supporting Information). The anomalous Hall angle obtained by applying an out-of-plane magnetic field to CoFe in our own devices is 1.5%.…”