Olena Gomonay

High antiferromagnetic domain wall velocity induced by Néel spin-orbit torques

We demonstrate the possibility to drive an antiferromagnet domain-wall at high velocities by field-like Néel spin-orbit torques. Such torques arise from current-induced local fields that alternate their orientation on each sub-lattice of the antiferromagnet and whose orientation depend primarily on the current direction, giving them their field-like character. The domain-wall velocities that can be achieved by this mechanism are two orders of magnitude greater than the ones in ferromagnets. This arises from the efficiency of the staggered spin-orbit fields to couple to the order parameter and from the exchange-enhanced phenomena in antiferromagnetic texture dynamics, which leads to a low domain-wall effective mass and the absence of a Walker break-down limit. In addition, because of its nature, the staggered spin-orbit field can lift the degeneracy between two 180◦ rotated states in a collinear antiferromagnet and provides a force that can move such walls and control the switching of the states.We demonstrate the possibility to drive an antiferromagnetic domain wall at high velocities by fieldlike Néel spin-orbit torques. Such torques arise from current-induced local fields that alternate their orientation on each sublattice of the antiferromagnet and whose orientation depends primarily on the current direction, giving them their fieldlike character. The domain wall velocities that can be achieved by this mechanism are 2 orders of magnitude greater than the ones in ferromagnets. This arises from the efficiency of the staggered spin-orbit fields to couple to the order parameter and from the exchange-enhanced phenomena in antiferromagnetic texture dynamics, which leads to a low domain wall effective mass and the absence of a Walker breakdown limit. In addition, because of its nature, the staggered spin-orbit field can lift the degeneracy between two 180° rotated states in a collinear antiferromagnet, and it provides a force that can move such walls and control the switching of the states.

Phenomenology of current-induced skyrmion motion in antiferromagnets

We study current-driven skyrmion motion in uniaxial thin film antiferromagnets in the presence of the Dzyaloshinskii-Moriya interactions and in an external magnetic field. We phenomenologically include relaxation and current-induced torques due to both spin-orbit coupling and spatially inhomogeneous magnetic textures in the equation for the Neel vector of the antiferromagnet. Using the collective coordinate approach we apply the theory to a two-dimensional antiferromagnetic skyrmion and estimate the skyrmion velocity under an applied DC electric current.

Concepts of antiferromagnetic spintronics

Antiferromagnetic spintronics is an emerging research field whose focus is on the electrical, optical or other means of control of the antiferromagnetic order parameter and its utility in information technology devices. An example of recently discovered new concepts is the Neel spin–orbit torque which allows for the antiferromagnetic order parameter to be controlled by an electrical current in common microelectronic circuits. In this review we discuss the utility of antiferromagnets as active and supporting materials for spintronics, the interplay of antiferromagnetic spintronics with other modern research fields in condensed matter physics, and its utility in future ”More than Moore” information technologies.

Berry-phase effects and electronic dynamics in a noncollinear antiferromagnetic texture

Abstract Antiferromagnets (AFMs), in contrast to ferromagnets, show a nontrivial magnetic structure with zero net magnetization. However, they share a number of spintronic effects with ferromagnets, including spin-pumping and spin transfer torques. Both phenomena stem from the coupled dynamics of free carriers and localized magnetic moments. In the present paper I study the adiabatic dynamics of a spin-polarized electrons in a metallic AFM exhibiting a noncollinear 120 magnetic structure. I show that the slowly varying AFM spin texture produces a non-Abelian gauge potential related to the time/space gradients of the Néel vectors. Corresponding emergent electric and magnetic fields induce rotation of spin and influence the orbital dynamics of free electrons. I discuss both the possibility of a topological spin Hall effect in the vicinity of topological AFM solitons with nonzero curvature and rotation of the electron spin traveling through the AFM domain wall.

Spin colossal magnetoresistance in an antiferromagnetic insulator

Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal–insulator transition and has inspired extensive studies for decades1,2. Here we demonstrate an analogous spin effect near the Néel temperature, TN = 296 K, of the antiferromagnetic insulator Cr2O3. Using a yttrium iron garnet YIG/Cr2O3/Pt trilayer, we injected a spin current from the YIG into the Cr2O3 layer and collected, via the inverse spin Hall effect, the spin signal transmitted into the heavy metal Pt. We observed a two orders of magnitude difference in the transmitted spin current within 14 K of the Néel temperature. This transition between spin conducting and non-conducting states was also modulated by a magnetic field in isothermal conditions. This effect, which we term spin colossal magnetoresistance (SCMR), has the potential to simplify the design of fundamental spintronics components, for instance, by enabling the realization of spin-current switches or spin-current-based memories.In the antiferromagnetic insulator Cr2O3 a strong modulation of the spin conduction with magnetic field near the Néel temperature is measured. By analogy with its charge counterpart, this effect is termed spin colossal magnetoresistance.

Skyrmions and multi-sublattice helical states in a frustrated chiral magnet

We investigate the existence and stability of skyrmions in a frustrated chiral ferromagnet by considering the competition between ferromagnetic (FM) nearest-neighbour (NN) interaction (

Manipulating antiferromagnets with magnetic fields: Ratchet motion of multiple domain walls induced by asymmetric field pulses

J_1

Controlling the switching field in nanomagnets by means of domain-engineered antiferromagnets

) and antiferromagnetic (AFM) next-nearest-neighbour (NNN) interaction (

Spin caloric effects in antiferromagnets assisted by an external spin current

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Combined effect of magnetic field and charge current on antiferromagnetic domain-wall dynamics

). Contrary to the general wisdom that long-range ferromagnetic order is not energy preferable under frustration, the skyrmion lattice not only exists but is even stable for a large field range when