Observation of magnetic vortex pairs at room temperature in a planar α-Fe2O3/Co heterostructure

Abstract

Vortices, occurring whenever a flow field 'whirls' around a one-dimensional core, are among the simplest topological structures, ubiquitous to many branches of physics. In the crystalline state, vortex formation is rare, since it is generally hampered by long-range interactions: in ferroic materials (ferromagnetic and ferroelectric), vortices are observed only when the effects of the dipole-dipole interaction are modified by confinement at the nanoscale, or when the parameter associated with the vorticity does not couple directly with strain . Here, we observe an unprecedented form of vortices in antiferromagnetic haematite (α-FeO) epitaxial films, in which the primary whirling parameter is the staggered magnetization. Remarkably, ferromagnetic topological objects with the same vorticity and winding number as the α-FeO vortices are imprinted onto an ultra-thin Co ferromagnetic over-layer by interfacial exchange. Our data suggest that the ferromagnetic vortices may be merons (half-skyrmions, carrying an out-of plane core magnetization), and indicate that the vortex/meron pairs can be manipulated by the application of an in-plane magnetic field, giving rise to large-scale vortex-antivortex annihilation.

Seeing is believing: visualization of antiferromagnetic domains

“…AFM Z 6 vortex/antivortex domains have been reported in a thin film of α-Fe 2 O 3 (hematite) whereas bulk crystals of α-Fe 2 O 3 do not seem to exhibit them. 29,30 The α-Fe 2 O 3 magnetic vortex/antivortex domains resemble crystallographic vortex/antivortex domains observed in, for example, hexagonal R(Mn,Fe) O 3 (R = rare earths), Fe 1/3 TaS 2 , and Ca 2 SrTi 2 O 7 . [31][32][33][34] It is a theoretical and experimental challenge to unveil such AFM vortex/antivortex domains.…”

Electrical Switching of Tristate Antiferromagnetic Néel Order in α−Fe2O3 Epitaxial Films

“…30 Figure 1b shows a 2/ X-ray diffraction (XRD) scan of a phase-pure α-Fe2O3(30 nm) epitaxial film on Al2O3(001), where the Laue oscillations of the α-Fe2O3(006) peak in the inset indicate its high crystal quality. The 30,31 We pattern our Pt(2 nm)/α-Fe2O3(30nm) bilayers into 8leg Hall crosses using photolithography and ion etching, as shown in Figs. 2b and 2c, where the width of the two vertical Hall terminals is 5 μm and the other six legs (60 apart) are 10 μm wide.…”

Tuning of non-paraxial effects of the Laguerre-Gaussian beam interacting with the two-component Bose–Einstein condensates

“…The vortex-antivortex superpositions appear as the counter-rotating persistent currents in superconducting circuits [66,67] which are propitious candidates for qubits in quantum-information processing and quantum communication networks [68]. Also, the vortices and multiple-vortices have been the subject of intensive experimental research in trapped superfluid Fermi gases [69][70][71] and even in real condensed matter system [72]. We believe this is one of the best approaches to study the effect of the non-paraxial nature of the vortex beam on ultra-cold atoms.…”