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Register a new userThe domain-wall motion driven by a rotating field in a ferrimagnet
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We theoretically study a ferrimagnetic domain-wall motion driven by a rotating magnetic field. We find that, depending on the magnitude and the frequency of the rotating field, the dynamics of a ferrimagnetic domain wall can be classified into two regimes. First, when the frequency is lower than a certain critical frequency set by the field magnitude, there is a stationary solution for the domain-wall dynamics, where a domain-wall in-plane magnetization rotates in-phase with the external field. The field-induced precession of the domain wall gives rise to the translational motion of the domain wall via the gyrotropic coupling between the domain-wall angle and position. In this so-called phase-locking regime, a domain-wall velocity increases as the frequency increases. Second, when the frequency exceeds the critical frequency, a domain-wall angle precession is not synchronous with the applied field. In this phase-unlocking regime, a domain wall velocity decreases as the frequency increases. Moreover, the direction of the domain-wall motion is found to be reversed across the angular compensation point where the net spin density of the ferrimagnet changes its sign. Our work suggests that the dynamics of magnetic solitons under time-varying biases may serve as platform to study critical phenomena.
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We theoretically study domain wall motion induced by an electric field in the quantum anomalous Hall states on a two-dimensional Kagome lattice with ferromagnetic order and spin-orbit coupling. We show that an electric charge is accumulated near the domain wall which indicates that the electric field drives both the accumulated charge and the domain wall with small energy dissipation. Using the linear response theory we compute the non-equilibrium spin density which exerts a non-adiabatic spin transfer torque on textures of the local magnetization. This torque emerges even when the bulk is insulating and does not require the longitudinal electric current. Finally, we estimate the velocity of domain wall motion in this system, which is faster than that in conventional metals.
Due to the difficulty in detecting and manipulating magnetic states of antiferromagnetic materials, studying their switching dynamics using electrical methods remains a challenging task. In this work, by employing heavy metal/rare earth-transition metal alloy bilayers, we experimentally studied current-induced domain wall dynamics in an antiferromagnetically coupled system. We show that the current-induced domain wall mobility reaches a maximum close to the angular momentum compensation. With experiment and modelling, we further reveal the internal structures of domain walls and the underlying mechanisms for their fast motion. We show that the chirality of the ferrimagnetic domain walls remains the same across the compensation points, suggesting that spin orientations of specific sublattices rather than net magnetization determine Dzyaloshinskii-Moriya interaction in heavy metal/ferrimagnet bilayers. The high current-induced domain wall mobility and the robust domain wall chirality in compensated ferrimagnetic material opens new opportunities for high-speed spintronic devices.
We study the domain wall motion in a disordered weak ferromagnet, induced by injecting a spin current from a strong ferromagnet. Starting from the spin diffusion equation describing the spin accumulation in the weak ferromagnet, we calculate the force and torque acting on the domain wall. We also study the ensuing domain wall dynamics, and suggest a possible measurement method for detecting the domain wall motion via measuring the additional resistance.
In easy-plane ferromagnets, all magnetic dynamics are restricted in a specific plane, and the domain wall becomes massive instead of gyroscopic. Here we show that the interaction between domain wall and spin wave packet in easy-plane ferromagnets takes analogy to two massive particles colliding via attraction. Due to mutual attraction, the penetration of spin wave packet leads to backward displacement of the domain wall, and further the penetration of continuous spin wave leads to constant velocity of domain wall. The underlying temporary exchange of momentum, instead of permanent transfer of linear and angular momenta, provides a new paradigm in magnonically driving domain wall.
Control of magnetic domain wall motion by electric fields has recently attracted scientific attention because of its potential for magnetic logic and memory devices. Here, we report on a new driving mechanism that allows for magnetic domain wall motion in an applied electric field without the concurrent use of a magnetic field or spin-polarized electric current. The mechanism is based on elastic coupling between magnetic and ferroelectric domain walls in multiferroic heterostructures. Pure electric-field driven magnetic domain wall motion is demonstrated for epitaxial Fe films on BaTiO$_3$ with in-plane and out-of-plane polarized domains. In this system, magnetic domain wall motion is fully reversible and the velocity of the walls varies exponentially as a function of out-of-plane electric field strength.
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