Magnetic Skyrmions in a Hall Balance with Interfacial Canted Magnetizations

Abstract

Magnetic skyrmions are attracting interest as efficient information‐storage devices with low energy consumption, and have been experimentally and theoretically investigated in multilayers including ferromagnets, ferrimagnets, and antiferromagnets. The 3D spin texture of skyrmions demonstrated in ferromagnetic multilayers provides a powerful pathway for understanding the stabilization of ferromagnetic skyrmions. However, the manipulation mechanism of skyrmions in antiferromagnets is still lacking. A Hall balance with a ferromagnet/insulating spacer/ferromagnet structure is considered to be a promising candidate to study skyrmions in synthetic antiferromagnets. Here, high‐density Néel‐type skyrmions are experimentally observed at zero field and room temperature by Lorentz transmission electron microscopy in a Hall balance (core structure [Co/Pt]n/NiO/[Co/Pt]n) with interfacial canted magnetizations because of interlayer ferromagnetic/antiferromagnetic coupling between top and bottom [Co/Pt]n multilayers, where the Co layers in [Co/Pt]n are always ferromagnetically coupled. Micromagnetic simulations show that the generation and density of skyrmions are strongly dependent on interlayer exchange coupling (IEC) and easy‐axis orientation. Direct experimental evidence of skyrmions in synthetic antiferromagnets is provided, suggesting that the proposed approach offers a promising alternative mechanism for room‐temperature spintronics.

Stacking-dependent nonreciprocal transport in magnetic skyrmions

“…I also show that interlayer antiferromagnetic exchange interaction is necessary to realize the ABC-stacking SkX by performing the simulated annealing for an effective spin model with the momentum-resolved interaction on a trilayer triangular lattice. The present results indicate that the stacking degree of freedom of the SkX is another important degree of freedom to control the nonreciprocal transport properties driven by the noncoplanar spin textures, which will be useful for other spin textures [57,58,59] and future spintronic applications based on skyrmions [60,61,62].…”

Suppression of Skyrmion Hall Motion in Antiferromagnets Driven by Circularly Polarized Spin Waves

“…where the first term is the AFM exchange interaction between the nearest neighbors with J > 0, m i is the local magnetic moment at site i, m i −S i /ħ with the local spin S i, and the reduced Plank constant ħ, the second term is the Dzyaloshinskii-Moriya interaction (DMI) between the nearest neighbors with the vector D D e ij , the third term is the perpendicular magnetic anisotropy with the easy z-axis and magnitude K. Considering the canted AFM sample KMnF 3 , which has been widely used in the study of spin wave propagation theoretically and experimentally [28][29][30], the parameters are chosen to be J 1.0 × 10 -21 J, D/J 0.14, and K/J 0.03 [31]. In addition, other AFM materials with stable existence of skyrmion and spin wave propagation such as two AFM coupled layers of YIG [26] and Co/Pt bilayer [12,32] could also be applicable to our simulation.…”

“…Recently, antiferromagnetic (AFM) skyrmion has been predicted theoretically [11] and observed experimentally at room temperatures in synthetic antiferromagnets [12]. AFM skyrmion is comprised of two coupled spin configurations with opposite topological numbers, and two Magnus forces respectively acting on two sub-lattices under spin-polarized current perfectly cancel with each other, allowing the motion straightly along the driving force [13][14][15][16].…”

Highly efficient heat-dissipation power driven by ferromagnetic resonance in MFe2O4 (M = Fe, Mn, Ni) ferrite nanoparticles

“…Since the FMR effect was experimentally discovered in the 1940s 1 , 2 , FMR measurement techniques have been used to probe magnetization excitations in many magnetic systems including magnetic thin films 3 and magnetic dots of different shapes such as finite rectangular elements 4 , 5 , circular nanodots 6 , and magnetic nanowires 7 . Magnetization excitation and the attendant relaxation processes in finite-dimension magnetic systems result in a variety of dynamic motions such as magnetic domain-wall motions 8 , 9 , many spin-wave modes 10 , 11 , and novel dynamic motions of magnetic vortices 12 and skyrmions 13 . Furthermore, research interest in the magneto-thermal effect, which represents the conversion of magnetostatic energy to heat due to intrinsic damping, recently has grown.…”