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Register a new userSpin-Orbit Torque Switching of Noncollinear Antiferromagnetic Antiperovskite Manganese Nitride Mn$_3$GaN
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Noncollinear antiferromagnets have promising potential to replace ferromagnets in the field of spintronics as high-density devices with ultrafast operation. To take full advantage of noncollinear antiferromagnets in spintronics applications, it is important to achieve efficient manipulation of noncollinear antiferromagnetic spin. Here, using the anomalous Hall effect as an electrical signal of the triangular magnetic configuration, spin-orbit torque switching with no external magnetic field is demonstrated in noncollinear antiferromagnetic antiperovskite manganese nitride Mn$_3$GaN at room temperature. The pulse-width dependence and subsequent relaxation of Hall signal behavior indicate that the spin-orbit torque plays a more important role than the thermal contribution due to pulse injection. In addition, multistate memristive switching with respect to pulse current density was observed. The findings advance the effective control of noncollinear antiferromagnetic spin, facilitating the use of such materials in antiferromagnetic spintronics and neuromorphic computing applications.
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We report electrical current switching of noncollinear antiferromagnetic (AFM) Mn$_3$GaN/Pt bilayers at room temperature. The Hall resistance of these bilayers can be manipulated by applying a pulse current of $1.5times10^6$~A/cm$^2$, whereas no significant change is observed up to $sim10^8$~A/cm$^2$ in Mn$_3$GaN single films, indicating that the Pt layer plays an important role. In comparison with ferrimagnetic Mn$_3$GaN/Pt bilayers, a lower electrical current switching of noncollinear AFM Mn$_3$GaN is demonstrated, with a critical current density two orders of magnitude smaller. Our results highlight that a combination of a noncollinear AFM antiperovskite nitride and a spin-torque technique is a good platform of AFM spintronics.
The anomalous Nernst effect (ANE) - the generation of a transverse electric voltage by a longitudinal heat current in conducting ferromagnets or antiferromagnets - is an appealing approach for thermoelectric power generation in spin caloritronics. The ANE in antiferromagnets is particularly convenient for the fabrication of highly efficient and densely integrated thermopiles as lateral configurations of thermoelectric modules increase the coverage of heat source without suffering from the stray fields that are intrinsic to ferromagnets. In this work, using first-principles calculations together with a group theory analysis, we systematically investigate the spin order-dependent ANE in noncollinear antiferromagnetic Mn-based antiperovskite nitrides Mn$_{3}X$N ($X$ = Ga, Zn, Ag, and Ni). The ANE in Mn$_{3}X$N is forbidden by symmetry in the R1 phase but amounts to its maximum value in the R3 phase. Among all Mn$_{3}X$N compounds, Mn$_{3}$NiN presents the most significant anomalous Nernst conductivity of 1.80 AK$^{-1}$m$^{-1}$ at 200 K, which can be further enhanced if strain, electric, or magnetic fields are applied. The ANE in Mn$_{3}$NiN, being one order of magnitude larger than that in the famous Mn$_{3}$Sn, is the largest one discovered in antiferromagnets so far. The giant ANE in Mn$_{3}$NiN originates from the sharp slope of the anomalous Hall conductivity at the Fermi energy, which can be understood well from the Mott relation. Our findings provide a novel host material for realizing antiferromagnetic spin caloritronics which promises exciting applications in energy conversion and information processing.
Non-collinear antiferromagnets exhibits richer magneto-transport properties due to the topologically nontrivial spin structure they possess compared to conventional nonmagnetic materials, which allows us to manipulate the charge-spin conversion more freely by taking advantage of the chirality. In this work, we explore the unconventional spin orbit torque of L1$_2$-ordered Mn$_3$Pt with a triangular spin structure. We observed an unconventional spin orbit torque along the $mathbf{x}$-direction for the (001)-oriented L1$_2$ Mn$_3$Pt, and found that it has a unique sign reversal behavior relative to the crystalline orientation. This generation of unconventional spin orbit torque for L1$_2$-ordered Mn$_3$Pt can be interpreted as stemming from the magnetic spin Hall effect. This report help clarify the correlation between the topologically nontrivial spin structure and charge-spin conversion in non-collinear antiferromagnets.
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.
The ability to switch magnetic elements by spin-orbit-induced torques has recently attracted much attention for a path towards high-performance, non-volatile memories with low power consumption. Realizing efficient spin-orbit-based switching requires harnessing both new materials and novel physics to obtain high charge-to-spin conversion efficiencies, thus making the choice of spin source crucial. Here we report the observation of spin-orbit torque switching in bilayers consisting of a semimetallic film of 1T-MoTe2 adjacent to permalloy. Deterministic switching is achieved without external magnetic fields at room temperature, and the switching occurs with currents one order of magnitude smaller than those typical in devices using the best-performing heavy metals. The thickness dependence can be understood if the interfacial spin-orbit contribution is considered in addition to the bulk spin Hall effect. Further threefold reduction in the switching current is demonstrated with resort to dumbbell-shaped magnetic elements. These findings foretell exciting prospects of using MoTe2 for low-power semimetal material based spin devices.
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