Creation of a Chiral Bobber Lattice in Helimagnet-Multilayer Heterostructures.

Kejing Ran,Yao Guang,Guoqiang Yu,Shilei Zhang,David M Burn,Yizhou Liu,Thorsten Hesjedal,Gerrit Van Der Laan,Haifeng Du

doi:10.1103/physrevlett.126.017204

Abstract

A chiral bobber is a localized three-dimensional magnetization configuration, terminated by a singularity. Chiral bobbers coexist with magnetic skyrmions in chiral magnets, lending themselves to new types of skyrmion-complementary bits of information. However, the on-demand creation of bobbers, as well as their direct observation remained elusive. Here, we introduce a new mechanism for creating a stable chiral bobber lattice state via the proximity of two skyrmion species with comparable size. This effect is experimentally demonstrated in a Cu_{2}OSeO_{3}/[Ta/CoFeB/MgO]_{4} heterostructure in which an exotic bobber lattice state emerges in the phase diagram of Cu_{2}OSeO_{3}. To unambiguously reveal the existence of the chiral bobber lattice state, we have developed a novel characterization technique, magnetic truncation rod analysis, which is based on resonant elastic x-ray scattering.

Highlights

A chiral bobber is a localized three-dimensional magnetization configuration, terminated by a singularity
This effect is experimentally demonstrated in a Cu2OSeO3=1⁄2Ta=CoFeB=MgO4 heterostructure in which an exotic bobber lattice state emerges in the phase diagram of Cu2OSeO3
To unambiguously reveal the existence of the chiral bobber lattice state, we have developed a novel characterization technique, magnetic truncation rod analysis, which is based on resonant elastic x-ray scattering

Summary

Published by the American Physical Society

(iii) At higher fields above BA2, a metastable surface state, i.e., the chiral bobbers (ChBs), which represent a new type of 3D topological texture, can be generated through a nonequilibrium process [5,13]. Chiral bobbers are characterized by a distinct 3D structure, resembling a floating bobber, that consists of a skyrmion stack with continuously reducing diameter away from the surface with a bobber length Lp, eventually shrinking down to a singularity, the Bloch point (BP) [5] Such a topological point defect has finite energy, revealing itself as a metastable state at fields larger than BA2, where the conical phase dominates [5,13]. The mechanism that stabilizes ChBs largely relies on their metastable nature, i.e., they can be produced by either field-cooling or field-tilting protocols [13] In both scenarios, bobbers seem to randomly nucleate at arbitrary positions within the surface [13].

ChBL SkTL

The quantity Min the structure factor FðqÞ can be expressed as