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Register a new userSpin-current-related magnetoresistance in epitaxial Pt/Co bilayers in the presence of spin Hall effect and Rashba-Edelstein effect
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We analyze the experimentally obtained spin-current-related magnetoresistance in epitaxial Pt/Co bilayers by using a drift-diffusion model that incorporates both bulk spin Hall effect and interfacial Rashba-Edelstein effect (REE). The magnetoresistance analysis yields, for the Pt/Co interface, a temperature-independent Rashba parameter in the order of 1e-11 eV m that agrees with theoretical calculations, along with an effective interfacial REE thickness of several angstroms which is in overall consistency with our previous spin-orbit torque analysis. In particular, our results suggest that both bulk and interface charge-spin current inter-
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We have studied the spin Hall magnetoresistance (SMR), the magnetoresistance within the plane transverse to the current flow, of Pt/Co bilayers. We find that the SMR increases with increasing Co thickness: the effective spin Hall angle for bilayers with thick Co exceeds the reported values of Pt when a conventional drift-diffusion model is used. An extended model including spin transport within the Co layer cannot account for the large SMR. To identify its origin, contributions from other sources are studied. For most bilayers, the SMR increases with decreasing temperature and increasing magnetic field, indicating that magnon-related effects in the Co layer play little role. Without the Pt layer, we do not observe the large SMR found for the Pt/Co bilayers with thick Co. Implementing the effect of the so-called interface magnetoresistance and the textured induced anisotropic scattering cannot account for the Co thickness dependent SMR. Since the large SMR is present for W/Co but its magnitude reduces in W/CoFeB, we infer its origin is associated with a particular property of Co.
We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt, sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing interface conductance $G_{mathrm{i}}$ plays a crucial role in YIG$|$Pt bilayers. In particular, our data suggest a sign change in $G_{mathrm{i}}$ between $10,mathrm{K}$ and $300,mathrm{K}$. Additionally, we report a higher order Hall effect, which appears in thin Pt films on YIG at low temperatures.
We present the Co-Gd composition dependence of the spin-Hall magnetoresistance (SMR) and anisotropic magnetoresistance (AMR) for ferrimagnetic Co100-xGdx / Pt bilayers. With Gd concentration x, its magnetic moment increasingly competes with the Co moment in the net magnetization. We find a nearly compensated ferrimagnetic state at x = 24. The AMR changes sign from positive to negative with increasing x, vanishing near the magnetization compensation. On the other hand, the SMR does not vary significantly even where the AMR vanishes. These experimental results indicate that very different scattering mechanisms are responsible for AMR and SMR. We discuss a possible origin for the alloy composition dependence.
We investigate the spin-current transport through antiferromagnetic insulator (AFMI) by means of the spin-Hall magnetoressitance (SMR) over a wide temperature range in Pt/NiO/Y$_3$Fe$_5$O$_{12}$ (Pt/NiO/YIG) heterostructures. By inserting the AFMI NiO layer, the SMR dramatically decreases by decreasing the temperature down to the antiferromagnetically ordered state of NiO, which implies that the AFM order prevents rather than promotes the spin-current transport. On the other hand, the magnetic proximity effect (MPE) on induced Pt moments by YIG, which entangles with the spin-Hall effect (SHE) in Pt, can be efficiently screened, and pure SMR can be derived by insertion of NiO. The dual roles of the NiO insertion including efficiently blocking the MPE and transporting the spin current from Pt to YIG are outstanding compared with other antiferromagnetic (AFM) metal or nonmagnetic metal (NM).
We experimentally investigate the current-induced magnetization reversal in Pt/[Co/Ni]$_3$/Al multilayers combining the anomalous Hall effect and magneto-optical Kerr effect techniques in crossbar geometry. The magnetization reversal occurs through nucleation and propagation of a domain of opposite polarity for a current density of the order of 0.3 TA/m$^2$. In these experiments we demonstrate a full control of each stage: i)the {O}rsted field controls the domain nucleation and ii) domain-wall propagation occurs by spin torque from the Pt spin Hall effect. This scenario requires an in-plane magnetic field to tune the domain wall center orientation along the current for efficient domain wall propagation. Indeed, as nucleated, domain walls are chiral and Neel like due to the interfacial Dzyaloshinskii-Moriya interaction.
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