M agnetic   skyrmions are particle-like spin textures that have been observed in chiral bulk magnets 1-4 and asymmetric magnetic multilayers 5-14. Electrical currents and current-induced spin-orbit torques (SOTs) can be used to manipulate skyrmions in various metallic systems 2,7,8,10,14 , and such capabilities could be useful in the development of energy-efficient spintronic devices. Thermal effects can also be used to generate and manipulate skyrmions 15,16 , which could lead to the development of unconventional computing 17 and energy-harvesting 18 applications. These thermal effects are, however, difficult to observe in bulk samples and large-area films; therefore, microstructured devices need to be employed. Furthermore, the generation of skyrmions via a pure thermal effect 19-21 has not been experimentally demonstrated so far; moreover, whether the skyrmion motion driven by thermal gradients follows the direction of thermal diffusion or, oppositely, the direction of magnonic spin torque 15,20,22,23 remains an open question.   approach allows us to study the dynamics of skyrmions induced by a perpendicular magnetic field (μ 0 H ⊥), electrical current (j e), temperature (T) and temperature gradient (ΔT(x)). The magnetic imaging was conducted at the Fe L 3 edge Q6

Room-temperature skyrmions in magnetic multilayers are considered to be promising candidates for the next-generation spintronic devices. Several approaches have been developed to control skyrmions, but they either cause significant heat dissipation or require ultrahigh electric fields near the breakdown threshold. Here, we demonstrate electric-field control of skyrmions through strain-mediated magnetoelectric coupling in ferromagnetic/ferroelectric multiferroic heterostructures. We show the process of non-volatile creation of multiple skyrmions, reversible deformation and annihilation of a single skyrmion by performing magnetic force microscopy with in situ electric fields. Strain-induced changes in perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction strength are characterized experimentally. These experimental results, together with micromagnetic simulations, demonstrate that strain-mediated magnetoelectric coupling (via strain-induced changes in both the perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction is responsible for the observed electric-field control of skyrmions. Our work provides a platform to investigate electric-field control of skyrmions in multiferroic heterostructures and paves the way towards more energy-efficient skyrmion-based spintronics.

Memristors, demonstrated by solid-state devices with continuously tunable resistance, [1][2][3][4][5][6][7] have emerged as a new paradigm for self-adaptive networks that require synapse-like functions (artificial synapse, for example). Spin-based memristors offer advantages over other types of memristors because of their significant endurance and high energy efficiency. [8,9] Yet, it remains a challenge to build dense and functional spintronic memristors with structures and materials that are compatible with existing ferromagnetic devices. [10] Here, a memristive device based upon Ta/CoFeB/MgO heterostructures is demonstrated, which are commonly used in out-of-plane magnetized magnetic tunnel junctions. [11] To achieve the memristive function, a domain wall (DW) is driven back and forth in a continuous manner in the CoFeB layer by applying in-plane positive or negative current pulses along the Ta layer, utilizing the spin-orbit torque (SOT) that the current exerts on the CoFeB magnetization. [12][13][14][15][16][17] Hence, Memristors, demonstrated by solid-state devices with continuously tunable resistance, have emerged as a new paradigm for self-adaptive networks that require synapse-like functions (artificial synapse, for example). Spin-based memristors offer advantages over other types of memristors because of their significant endurance and high energy efficiency. Yet it remains a challenge to build dense and functional spintronic memristors with structures and materials that are compatible with existing ferromagnetic devices. Here, a memristive device based upon Ta/CoFeB/MgO heterostructures is demonstrated, which are commonly used in out-of-plane magnetized magnetic tunnel junctions (MTJ). To achieve the memristive function, a domain wall (DW) is driven back and forth in a continuous manner in the CoFeB layer by applying in-plane positive or negative current pulses along the Ta layer, utilizing the spin-orbit torque (SOT) that the current exerts on the CoFeB magnetization. Hence, the magnetization and consequently the anomalous Hall effect (AHE) resistance are modulated in an analog manner, being controlled by the pulsed current characteristics including amplitude, duration, and repetition number. The quasi-continuous AHE resistance variation is explained by the SOT-induced DW creep motion. These results pave the way for developing SOT-based energy-efficient neuromorphic systems.

No abstract

In this letter, spin rectification was used to study the electric field controlled dynamic magnetic properties of the multiferroic composite which is a Co stripe with induced in-plane anisotropy deposited onto a Pb(Mg1∕3Nb2∕3)O3-PbTiO3 substrate. Due to the coupling between piezoelectric and magnetoelastic effects, a reversible in-plane anisotropy switching has been realized by varying the history of the applied electric field. This merit results from the electric hysteresis of the polarization in the nonlinear piezoelectric regime, which has been proved by a butterfly type electric field dependence of the in-plane anisotropy field. Moreover, the electric field dependent effective demagnetization field and linewidth have been observed at the same time.