Current‐Controlled Topological Magnetic Transformations in a Nanostructured Kagome Magnet

Abstract

Topological magnetic charge Q is a fundamental parameter that describes the magnetic domains and determines their intriguing electromagnetic properties. The ability to switch Q in a controlled way by electrical methods allows for flexible manipulation of electromagnetic behavior in future spintronic devices. Here, the room‐temperature current‐controlled topological magnetic transformations between Q = −1 skyrmions and Q = 0 stripes or type‐II bubbles in a kagome crystal Fe3Sn2 are reported. It is shown that reproducible and reversible skyrmion–bubble and skyrmion–stripe transformations can be achieved by tuning the density of nanosecond pulsed current of the order of ≈1010 A m−2. Further numerical simulations suggest that spin‐transfer torque combined with Joule thermal heating effects determine the current‐induced topological magnetic transformations.

Magnetic Skyrmionic Bubbles at Room Temperature and Sign Reversal of the Topological Hall Effect in a Layered Ferromagnet Cr0.87Te

“…In these materials, such as manganite La 1– x Sr x MnO 3 ( x = 0.175) and La 2–2 x Sr 1+2 x Mn 2 O 7 ( x = 0.315), hexagonal MnNiGa alloy, and Fe 3 Sn 2 kagome alloy, − the mutual competition in UMA, dipole–dipole interaction, and ferromagnetic exchange interaction can form various magnetic bubble domains including topological skyrmionic bubbles, which are described by two degrees of freedom, i.e., helicity and vorticity. These bubbles with distinct internal structures show diverse dynamics of Bloch lines and can be feasibly manipulated by external stimuli. , Recently, magnetic skyrmions were observed in centrosymmetric van der Waals (vdW) two-dimensional (2D) Fe 3 GeTe 2 and Cr 2 Ge 2 Te 6 crystals, − which prompts the realization of peculiar quantum states and design of low-dimensional spintronic devices. However, the long-range ferromagnetic ordering in these vdW 2D crystals only survives far below room temperature. − …”

Current-driven dynamics of skyrmion bubbles in achiral uniaxial magnets

“…[13][14][15][16][17] Besides, skyrmions (also called skyrmion bubbles) can be also stabilized by dipole-dipole interactions in centrosymmetric uniaxial magnets. [2,[18][19][20][21][22][23][24][25] There are two types of bubbles in centrosymmetric uniaxial magnets, i.e. type-I skyrmion bubble and type-II topologically-trivial bubble.…”

“…[24] Because of the absence of chiral interactions, skyrmion bubbles in the centrosymmetric magnets are achiral and have two helictites at a given field. [19,20] Achiral skyrmion bubbles have been found in many room-temperature centrosymmetric ferromagnets, such as Fe3Sn2 [22,26] , Fe/Gd [20] , and BaFeScMgO. [21] The size of achiral skyrmion bubbles can be as small as ~50 nm and is comparable with room-temperature chiral skyrmions.…”

“…Recent studies have shown current-induced emergent dynamic manipulations of achiral skyrmion bubbles, such as topological skyrmion-bubble transformations. [19,30] However, the current-induced coherent dynamic motions and their physical mechanisms of achiral skyrmion bubbles are less demonstrated.…”

Deterministic generation of skyrmions and antiskyrmions by electric current

“…The skyrmion and antiskyrmion are linked by time reversal operation, and therefore the application of external magnetic field determines if the skyrmions or antiskyrmions are stabilized in the system. The previous study on the electrical generation of skyrmions requires external magnetic fields [15][16][17][18][19][20][21][22][23][24], which in turn determine the topological charge of the created skyrmions. Furthermore, the static magnetic field required to stabilize magnetic skyrmion complicates the device design and increases the energy consumption.…”