A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

Abstract

Magnetic skyrmions are topologically protected vortex-like nanometric spin textures that have recently received growingly attention for their potential applications in future highperformance spintronic devices. Such unique mangetic naondomains have been recently discovered in bulk chiral magnetic materials, such as MnSi [1][2][3][4] , FeGe [5,6] , FeCoSi [7] , Cu 2 OSeO 3 [8][9][10] , -Mn-type Co-Zn-Mn [11] , and also GaV 4 S 8[12] a polar magnet. The crystal structure of these materials is cubic and lack of centrosymmetry, leading to the existence of Dzyaloshinskii-Moriya (DM) interactions. Unlike the conventional spin configurations, such as helical or conical, that are usually found in chiral magnets, a magnetic skyrmion has a particle-like swirling-spin configuration characterized by a topological index called the skyrmion number [13,14] . The nontrivial topology of magnetic skyrmions results in a number of

Generation of high-density biskyrmions by electric current

“…8 and termed as MnNiGa in this paper. The thin plates for Lorentz TEM observations are cut from bulk samples and thinned by mechanical polishing and argon-ion milling.…”

“…Recently, we have indeed observed the Bloch-type biskyrmions in a centrosymmetric (Mn 1−x Ni x ) 65 Ga 35 (x = 0.5) (MnNiGa) alloy, which can survive over a wide temperature (T) range from 100 to 340 K. 8 Unfortunately, in this alloy, magnetic field can indeed induce some biskyrmions, but the density of biskyrmions is low and no well-ordered biskyrmion arrangement (lattice) is possible at room temperature. Along this line, any manipulation of these scattered biskyrmions into a high-density biskyrmion lattice is definitely appealing for skyrmion-dependent applications in highdensity information storage.…”

“…[4][5][6] Exploring new materials to overcome the temperature limitation is the everlasting pursuit. Roomtemperature skyrmions have been discovered in centrosymmetric magnets where the magnetic dipolar interaction is dominant, 7,8 in magnetic multilayers with enhanced interfacial DMI, 1,9 and in the artificial skyrmion systems. 10,11 Usually, the spin configuration in bulk magnets is typically the Bloch-type "spiral" skyrmion where the swirling direction is perpendicular to the radial direction, as opposed to the Néel-type "hedgehog" skyrmion where the swirling direction is in the radial plane, as commonly found in ultrathin magnetic films.…”

Crystal-orientation dependence of magnetic domain structures in the skyrmion-hosting magnets MnNiGa

“…For example, a new type of spin structure composed of two single skyrmions with opposite vorticity, called a biskyrmion, has been experimentally observed in La− −Sr− −Mn− −O 18 and hexagonal Mn− −Ni− −Ga. 19 Moreover, Yu et al 20 have found a variety of spin textures in the La 1−x Sr x MnO 3 (x = 0.175). Therefore, the magnetic skyrmions with variable spin textures in these centrosymmetric magnets may open a new pathway to the future technological applications.…”

Formation and stability of metastable skyrmionic spin structures with various topologies in an ultrathin film

“…In contrast, dipolar systems allow for two helicity values which are degenerate in energy [16], while in frustrated systems a continuous degeneracy arises [36,37]. Furthermore, the presence of biskyrmions (bound pairs of skyrmions) was recently demonstrated in several centrosymmetric materials [17,38,39]. In frustrated systems, skyrmionic structures with different topological charges have been identified in numerical calculations and simulations [36,37,40].…”