3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots

Abstract

Magnetic skyrmions are widely attracting researchers due to fascinating physics and novel applications related to their non-trivial topology. Néel skyrmions have been extensively investigated in magnetic systems with Dzyaloshinskii–Moriya interaction (DMI) and/or perpendicular magnetic anisotropy. Here, by means of micromagnetic simulations and analytical calculations, we show that 3D quasi-skyrmions of Néel type, with topological charge close to 1, can exist as metastable states in soft magnetic nanostructures with no DMI, such as in Permalloy thick cylindrical and dome-shaped nanodots. The key factor responsible for the stabilization of DMI-free is the interplay of the exchange and magnetostatic energies in the nanodots. The range of geometrical parameters where the skyrmions are found is wider in magnetic dome-shape nanodots than in their cylindrical counterparts. Our results open the door for a new research line related to the nucleation and stabilization of magnetic skyrmions in a broad class of nanostructured soft magnetic materials.

Symmetry Breaking-Induced Resonance Dynamics in Bloch Point Nanospheres: Unveiling Magnetic Volume Effects and Geometric Parameters for Advanced Applications in Magnetic Sensing and Spintronics

“…In other words, the invariant Q measures how many times the magnetization fields cover the unitary sphere. Similarly, 3D systems also present topological magnetic textures. − Due to recent advances in producing and characterizing more sophisticated structures with different shapes and sizes, exploring the topological properties of 3D magnetic textures has become a key ingredient for proposals based on controlling magnetic solitons for use as information carriers. , Examples of 3D magnetic textures include skyrmion tubes, hopfions, torons, and Bloch points (BPs). , Similar to the 2D magnetic configurations mentioned above, they exhibit topological features quantified by an integer value of Q and nonzero 3D topological charge , (Hopf index). Nevertheless, the Hopf index, the 3D counterpart of the topological invariant Q , remains inconclusive for most cases, except for the hopfion and BP cases.…”

3D Magnetization Textures: Toroidal Magnetic Hopfion Stability in Cylindrical Samples

“…[ 20 , 21 , 22 ], describing magnetic hopfions in thick cylindrical dots, without explanations of its importance. I note that the magnetostatic interaction can also lead to the stabilization of other kinds of complicated magnetization textures: the Bloch point hopfions with non-zero Hopf index or half-hedgehog (3D quasi-skyrmion) magnetization textures, even in soft magnetic materials with no DMI [ 23 , 24 ].…”

Magnetostatic interaction between Bloch point nanospheres

“…Up to recent years, the interest was centered in studying solitons lying in quasi-2D-systems, such as skyrmions 7 , skyrmioniums 8 , biskyrmions 9 , and bimerons 10 – 13 . Nevertheless, recent advances in producing and characterizing nano and microstructures with a plethora of shapes and sizes 14 – 17 renewed the interest in describing the properties of three-dimensional (3D) magnetic profiles 18 – 27 . Among the 3D magnetic quasiparticles with topological protection, we can highlight the Bloch point (BP) 28 , 29 , which is a structure that presents a singular point at its center, where ferromagnetic order is destroyed 30 – 32 .…”