Topological spin-hedgehog crystals of a chiral magnet as engineered with magnetic anisotropy

Abstract

We report the engineering of spin-hedgehog crystals in thin films of the chiral magnet MnGe by tailoring the magnetic anisotropy. As evidenced by neutron scattering on films with different thicknesses and with varying magnetic field, we can realize continuously deformable spin-hedgehog crystals, each of which is described as a superposition state of a different set of three spin spirals (a triple-q state). The directions of the three propagation vectors q vary systematically, gathering from the three orthogonal 100 directions towards the film normal as the strength of the uniaxial magnetic anisotropy and/or the magnetic field applied along the film normal increase. The formation of triple-q states coincides with the onset of topological Hall signals, which is ascribed to skew scattering by emergent magnetic field originating in the non-trivial topology of spin hedgehogs.These findings highlight how nano-engineering of chiral magnets makes possible the rational design of unique topological spin textures. 72.15.Gd

Bulk and surface topological indices for a skyrmion string: current-driven dynamics of skyrmion string in stepped samples

“…In the three dimensional magnets, the skyrmion usually forms rod-like object along the external magnetic field [14][15][16][17][18][19][20][21][22][23][24][25] . When the meandering degree of freedom is introduced, it is better to consider it as skyrmion string.…”

“…2 Department of Applied Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. * email: wataru@riken.jp sometimes called (anti)hedgehog or (anti)monopole 14,16,[20][21][22]30 . In the present paper, we use the word, (anti) monopole, to express the topological defect on the skyrmion string.…”

Enhanced Magnetic Anisotropy and Orbital Symmetry Breaking in Manganite Heterostructures

“…For example, anisotropic magnetism in phase‐separated manganites directly links to magnetic inhomogeneity, where magnetic domains grow along one preferred crystal axis due to the anisotropic free‐energy landscape . In a magnetic system where the spin chirality is allowed, magnetic anisotropy plays a key role in determining the propagation direction of spin spirals and stabilizing subtle spin textures such as skyrmions . For spintronic devices, magnetic anisotropy is required to retrieve the information stored in an antiferromagnet and improves areal density of magnetic memories .…”

Direct Observation of the Statics and Dynamics of Emergent Magnetic Monopoles in a Chiral Magnet

“…The HL state is constructed by the superposition of three orthogonal proper-screw structures with propagation vectors (q 1 , q 2 , and q 3 ) aligned with the equivalent h100i directions [32,34]. Although the film is epitaxially grown along the [111] direction, there exist two crystalline domains with opposite chirality, which are related by a mirror operation with respect to the (111) plane [47]. As a result, not a threefold-, but instead a sixfold-symmetric pattern of scattering peaks appears around the [111] direction, along which H is also applied [ Fig.…”