Abstract
The spin Hall magnetoresistance (SMR) of Pt/FeCoB bilayers with in-plane magnetocrystalline anisotropy was analyzed with respect to a second-order effect in the sensing current, which acts, through the spin Hall effect in Pt, as a torque on the magnetization of the ferromagnetic (FM) layer and changes slightly its configuration. This leads to a small current-dependent shift of the SMR curves in field that allows, in structures with a multidomain state (e.g., Hall bars), the determination of the sign of the magnetic remanence. The SMR measurements were performed as a function of the Pt thickness and the spin Hall angle, and the diffusion length and the field-like and damping-like spin–orbit-torque (SOT) efficiency were determined. The results were compared with the values obtained from harmonic Hall voltage and SOT-FM resonance (FMR) measurements and show a good agreement.
Highlights
T HE current-induced spin–orbit torque (SOT) [1]–[4] is the physical phenomenon by which a magnetic moment current, generated by a heavy metal (HM) layer, induces a magnetic torque on a side ferromagnetic (FM) layer
We performed measurements of spin Hall magnetoresistance (SMR) in metallic heterostructures consisting of Pt/FeCoB with various Pt thicknesses and magnetocrystalline anisotropy in the film plane
The sensing current is not limited to the Pt layer due to the finite resistivity of the FM layer, the resistivity measurement can be almost exclusively ascribed to the SMR effect due to the large difference of the resistances and the anisotropic magnetoresistance (AMR) and SMR effects
Summary
T HE current-induced spin–orbit torque (SOT) [1]–[4] is the physical phenomenon by which a magnetic moment current (or spin current), generated by a heavy metal (HM) layer, induces a magnetic torque on a side ferromagnetic (FM) layer. By the comparison of the magnetoresistance signal obtained by the two current pulses of opposite sign, the spin–orbit field and the SOT efficiency can be evaluated In their work, the latter is obtained from magnetization switching experiments (i.e., magnetization reversal by the current in the HM) in Hall bars, an experiment that depends on the magnetization or domain configuration and dynamics in the Hall bar and on the strength of the SOT. As a function of field and electric current shows the influence of SOT on the magnetization state This analysis may help to read the remanence state and to investigate the performance of SOT even if the spin current generated by the spin Hall effect is not large enough to reverse the magnetization direction in an extended structure, such as a Hall bar
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