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تسجيل مستخدم جديدElectrical switching of antiferromagnetic CoO | Pt across the Neel temperature
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One of the most important challenges in antiferromagnetic spintronics is the read-out of the Neel vector state. High current densities up to 10$^8$ Acm$^{-2}$ used in the electrical switching experiments cause notorious difficulty in distinguishing between magnetic and thermal origins of the electrical signals. To overcome this problem, we present a temperature dependence study of the transverse resistance changes in the switching experiment with CoO|Pt devices. We demonstrate the possibility to extract a pattern of spin Hall magnetoresistance for current pulses density of $5 times 10^7$ Acm$^{-2}$ that is present only below the Neel temperature and does not follow a trend expected for thermal effects. This is the compelling evidence for the magnetic origin of the signal, which is observed using purely electrical techniques. We confirm these findings by complementary experiments in an external magnetic field. Such an approach can allow determining the optimal conditions for switching antiferromagnets and be very valuable when no imaging techniques can be applied to verify the origin of the electrical signal.
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We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop tran
sition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of $4x10^{-11} T A^{-1} m^2$. The Neel vector final state ($n perp j$) is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.
As electrical control of Neel order opens the door to reliable antiferromagnetic spintronic devices, understanding the microscopic mechanisms of antiferromagnetic switching is crucial. Spatially-resolved studies are necessary to distinguish multiple
nonuniform switching mechanisms; however, progress has been hindered by the lack of tabletop techniques to image the Neel order. We demonstrate spin Seebeck microscopy as a sensitive, table-top method for imaging antiferromagnetic order in thin films, and apply this technique to study spin-torque switching in NiO/Pt and Pt/NiO/Pt heterostructures. We establish the interfacial antiferromagnetic spin Seebeck effect in NiO as a probe of surface Neel order, resolving antiferromagnetic spin domains within crystalline twin domains. By imaging before and after applying current-induced spin torque, we resolve spin domain rotation and domain wall motion, acting simultaneously. We correlate the changes in spin Seebeck images with electrical measurements of the average Neel orientation through the spin Hall magnetoresistance, confirming that we image antiferromagnetic order.
We probe the current-induced magnetic switching of insulating antiferromagnet/heavy metals systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe swi
tching of more than one third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.
Understanding the electrical manipulation of antiferromagnetic order is a crucial aspect to enable the design of antiferromagnetic devices working at THz frequency. Focusing on collinear insulating antiferromagnetic NiO/Pt thin films as a materials p
latform, we identify the crystallographic orientation of the domains that can be switched by currents and quantify the Neel vector direction changes. We demonstrate electrical switching between different T-domains by current pulses, finding that the Neel vector orientation in these domains is along $[pm5 pm5 19]$, different compared to the bulk $<11bar{2}>$ directions. The final state of the Neel vector $textbf{n}$ switching after current pulses $textbf{j}$ along the $[1 pm1 0]$ directions is $textbf{n}parallel textbf{j}$. By comparing the observed Neel vector orientation and the strain in the thin films, assuming that this variation arises solely from magnetoelastic effects, we quantify the order of magnitude of the magnetoelastic coupling coefficient as $b_{0}+2b_{1}=3*10^7 J m^{-3}$ . This information is key for the understanding of current-induced switching in antiferromagnets and for the design and use of such devices as active elements in spintronic devices.
We report the direct observation of switching of the Neel vector of antiferromagnetic (AFM) domains in response to electrical pulses in micron-scale Pt/$alpha$-Fe$_2$O$_3$ Hall bars using photoemission electron microscopy. Current pulses lead to reve
rsible and repeatable switching, with the current direction determining the final state, consistent with Hall effect experiments that probe only the spatially averaged response. Current pulses also produce irreversible changes in domain structure, in and even outside the current path. In both cases only a fraction of the domains switch in response to pulses. Further, analysis of images taken with different x-ray polarizations shows that the AFM Neel order has an out-of-plane component in equilibrium that is important to consider in analyzing the switching data. These results show that -in addition to effects associated with spin-orbit torques from the Pt layer, which can produce reversible switching-changes in AFM order can be induced by purely thermal effects.
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