Abstract
Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. Here, we experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions in such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.
Highlights
Magnetic skyrmions are topologically stable particle-like spin textures
When an electric current is applied to the skyrmion system, the coupling between the non-trivial spin configuration of skyrmion and the electric current usually gives rise to interesting responses to magnetic field and electric field, such as emergent electromagnetic induction, skyrmion Hall effects,[9, 12] angular momentum exchange via the spin-transfer torque (STT),[2] and others
We demonstrate that, in the MnNiGa alloy, such a lattice can be properly generated by applying an electric current with the assistance of a magnetic field
Summary
Magnetic skyrmions are topologically stable particle-like spin textures. The manipulation of skymions by electric current, for example, the skyrmion dynamic behavior,[1,2,3] has been the focus of significant research. It should be mentioned that the critical magnetic field to form the biskyrmions can be influenced by the sample thickness, which be reduced if the electric current increases This dependence can be understood if one considers that the current-induced STT can change the microscopic domain configuration so that the longrange stable stripe ground state is gradually replaced by a series of metastable biskyrmions states when the system goes through the magnetic domain transition. Based on the corresponding Lorentz TEM imaging results, one may propose the schematic diagram in Fig. 4 where the evolution of high-density biskyrmions in response to electric current is summarized, in comparison with the evolution of conventional magnetic field-induced scattered biskyrmions. A comparison of all these procedures allows us to clearly see the advantages of the current-controlled procedures in manipulating the biskyrmion density, as proposed in this work, over the conventional procedures where only a magnetic field is used to induce the biskyrmions
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