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Magnetic vortices are topological spin structures frequently found in ferromagnets, yet novel to antiferromagnets. By combining experiment and theory, it is demonstrated that in a nanostructured antiferromagnetic‐ferromagnetic NiO(111)‐Fe(110) bilayer, a magnetic vortex is naturally stabilized by magnetostatic interactions in the ferromagnet and is imprinted onto the adjacent antiferromagnet via interface exchange coupling. Micromagnetic simulations are used to construct a corresponding phase diagram of the stability of the imprinted antiferromagnetic vortex state. The in‐depth analysis reveals that the interplay between interface exchange coupling and the antiferromagnet magnetic anisotropy plays a crucial role in locally reorienting the Néel vector out‐of‐plane in the prototypical in‐plane antiferromagnet NiO and thereby stabilizing the vortices in the antiferromagnet. Nanoscale magnetic vortex is naturally stabilized by magnetostatic interactions in the ferromagnet and is imprinted onto the adjacent antiferromagnet via interface exchange coupling. The interplay between interface exchange coupling and the antiferromagnet magnetic anisotropy plays a crucial role in locally reorienting the Néel vector out‐of‐plane in the prototypical in‐plane antiferromagnet NiO and thereby stabilizing the vortices in the antiferromagnet.

Exchange‐bias‐coupled spintronic terahertz emitters (EBC‐STEs) utilize an antiferromagnet (AFM) as both a passive pinning layer for ferromagnetic spins and a detector of spin currents. Conventionally, terahertz (THz) emission from spintronic terahertz emitters (STEs) is attributed solely to the ferromagnetic subsystem, with the ultrafast magnetization dynamics of AFM considered undetectable due to its zero net magnetic moment. Here, we demonstrate a novel experimental approach to probe and control ultrafast magnetization dynamics driven by laser‐induced optical torque on the Néel vector in collinear AFM MnPt. The Néel vector induced transient magnetization is isolated from ferromagnetic magnetization dynamics by detecting the distinct THz emission from the canted magnetic moment, as confirmed in Pt/MnPt bilayers. We further investigate the stability of the EBC‐STE compared to conventional STEs under optical excitation. This work provides direct evidence of ultrafast AFM magnetization dynamics in an EBC‐STE, transforming it from a passive emitter into a sensitive probe of interfacial ultrafast magnetism and unlocking the potential of antiferromagnetic THz spintronics. Direct evidence of ultrafast manipulation of the antiferromagnetic order parameter (Néel vector) in an exchange bias system is demonstrated using terahertz (THz) emission spectroscopy. Laser‐induced torque cants the Néel vector in the collinear antiferromagnet MnPt, generating a transient magnetic moment that produces THz radiation. This study provides an efficient mechanism for controlling antiferromagnetic spins with light.

Boron (B) alloying transforms the magnetoelectric antiferromagnet Cr2O3 into a multifunctional single‐phase material which enables electric field driven π/2 rotation of the Néel vector. Nonvolatile, voltage‐controlled Néel vector rotation is a much‐desired material property in the context of antiferromagnetic spintronics enabling ultralow power, ultrafast, nonvolatile memory, and logic device applications. Néel vector rotation is detected with the help of heavy metal (Pt) Hall‐bars in proximity of pulsed laser deposited B:Cr2O3 films. To facilitate operation of B:Cr2O3‐based devices in CMOS (compementary metal‐oxide semiconductor) environments, the Néel temperature, TN, of the functional film must be tunable to values significantly above room temperature. Cold neutron depth profiling and X‐ray photoemission spectroscopy depth profiling reveal thermally activated B‐accumulation at the B:Cr2O3/ vacuum interface in thin films deposited on Al2O3 substrates. The B‐enrichment is attributed to surface segregation. Magnetotransport data confirm B‐accumulation at the interface within a layer of ≈50 nm thick where the device properties reside. Here TN enhances from 334 K prior to annealing, to 477 K after annealing for several hours. Scaling analysis determines TN as a function of the annealing temperature. Stability of post‐annealing device properties is evident from reproducible Néel vector rotation at 370 K performed over the course of weeks. Boron (B) alloying transforms the magnetoelectric antiferromagnet Cr2O3 into a multifunctional material allowing for voltage‐controllable Néel vector rotation. Cold neutron and X‐ray photoemission depth profiling together with magnetotransport measurements reveal B‐accumulation at interfaces with the functional B:Cr2O3 films. The B‐enrichment is attributed to surface segregation and accompanied by significant TN enhancement making B:Cr2O3 a candidate material for voltage‐controlled antiferromagnetic spintronics.

We demonstrate analytically and numerically, that a thin film of an antiferromagnetic (AFM) material, having biaxial magnetic anisotropy and being driven by an external spin-transfer torque signal, can be used for the generation of ultra-short “Dirac-delta-like” spikes. The duration of the generated spikes is several picoseconds for typical AFM materials and is determined by the inplane magnetic anisotropy and the effective damping of the AFM material. The generated output signal can consist of a single spike or a discrete group of spikes (“bursting”), which depends on the repetition (clock) rate, amplitude, and shape of the external control signal. The spike generation occurs only when the amplitude of the control signal exceeds a certain threshold, similar to the action of a biological neuron in response to an external stimulus. The “threshold” behavior of the proposed AFM spike generator makes possible its application not only in the traditional microwave signal processing but also in the future neuromorphic signal processing circuits working at clock frequencies of tens of gigahertz.

Magnetic domains and the walls between are the subject of great interest because of the role they play in determining the electrical properties of ferromagnetic materials and as a means of manipulating electron spin in spintronic devices. However, much less attention has been paid to these effects in antiferromagnets, primarily because there is less awareness of their existence in antiferromagnets, and in addition they are hard to probe since they exhibit no net magnetic moment. In this paper, we discuss the electrical properties of chromium, which is the only elemental antiferromagnet and how they depend on the subtle arrangement of the antiferromagnetically ordered spins. X-ray measurement of the modulation wavevector Q of the incommensurate antiferromagnetic spin-density wave shows thermal hysteresis, with the corresponding wavelength being larger during cooling than during warming. The thermal hysteresis in the Q vector is accompanied with a thermal hysteresis in both the longitudinal and Hall resistivity. During cooling, we measure a larger longitudinal and Hall resistivity compared with when warming, which indicates that a larger wavelength at a given temperature corresponds to a smaller carrier density or equivalently a larger antiferromagnetic ordering parameter compared to a smaller wavelength. This shows that the arrangement of the antiferromagnetic spins directly influences the transport properties. In thin films, the sign of the thermal hysteresis for Q is the same as in thick films, but a distinct aspect is that Q is quantized.

In a collinear antiferromagnet, spins tend to cant towards the direction of an applied magnetic field, thereby decreasing the energy of the system. The canting angle becomes negligible when the magnetic field is small so that the induced anisotropic energy is substantially lower than the exchange energy. However, this tiny anisotropy can play a significant role when the intrinsic anisotropy of the antiferromagnet is small. In our work, we conduct direct imaging of the Néel vector in a two-dimensional easy-plane antiferromagnet, MnPSe\\(_3\\), with negligible spin canting under an external in-plane magnetic field. The small inherent in-plane anisotropy allows for the continuous rotation of the Néel vector by ramping up the magnetic field in samples from the bulk to the monolayer. In monolayer samples, the applied magnetic field elevates the Néel temperature 10\\(\\%\\) at 5 tesla, as the combination of intrinsic and field-induced anisotropies set a critical temperature scale for fluctuations of the otherwise disordered Néel vector field. Our study illuminates the contribution of field-induced anisotropy in two dimensional magnets with in-plane anisotropy. We also demonstrate that the strain can tune the spin flop transition field strength by one order of magnitude.