Imaging the spin chirality of ferrimagnetic Néel skyrmions stabilized on topological antiferromagnetic Mn3Sn

Abstract

Néel skyrmions are generally realized in asymmetric multilayers made of heavy metals (HMs) and ultrathin ferromagnets possessing strong interfacial Dzyaloshinskii-Moriya interactions (iDMIs). Depending on the relative strengths of iDMIs at the interfaces, various types of Néel skyrmions have been suggested, which are typified with characteristically different topological properties and current-driven dynamics. This suggests the importance of a precise quantification of their spin chiralities. In this paper, we explore the possibility of realizing Néel skyrmions in magnetic multilayers without the direct usage of standard HMs. Specifically, through depositing a thin layer of ferrimagnetic (FIM) CoTb layer on top of an antiferromagnetic (AFM) quantum material of composition Mn 3 Sn, the AFM exchange interaction at the asymmetric interface provides an equivalent iDMI for stabilizing FIM Néel skyrmions. Secondly, through using advanced four-dimensional Lorentz scanning transmission electron microscopy (4D LSTEM), in combination with x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM), we can directly determine the spin chirality of FIM Néel skyrmions. The present findings not only broaden the phase space for chiral interfacial magnetism but also provide a possibility for future applications of heavy-metal-free skyrmionic devices.

A room temperature polar magnetic metal

“…Magnetic induction field simulated from Bloch-type and Néel-type skyrmions were calculated from the magnetization distribution of an isolated skyrmion generated using the 360° domain wall model [33,55,56]. For simulation inputs, the diameter and domain wall widths of skyrmions are set to 90 nm and 4.2 nm, respectively.…”

“…Recent work reported that by capping a spinorbit coupling layer on Fe 3 GeTe 2 induces an interfacial DMI and skyrmions in this bilayer system below ambient temperature. [30][31][32][33] The Fe 5 GeTe 2 system exhibits two-dimensional (2D) itinerant ferromagnetism with high Curie temperature which provides an ideal platform to design such a metallic, polar magnetic material. The vdW Fe 5-x GeTe 2 magnet exhibits rhombohedral ABC stacking with a ferromagnetic ground state.…”

Quantum Sensing and Imaging of Spin–Orbit‐Torque‐Driven Spin Dynamics in the Non‐Collinear Antiferromagnet Mn3Sn

“…[17][18][19] Despite the enormous technological promise and rich fundamental physics of Mn 3 X compounds, the establishment of direct correlations between the micro-and mesoscopic magnetic structure and the intriguing properties of these materials remains elusive. These challenges are particularly apparent for nanometer-thick Mn 3 X films, [4][5][6][7][20][21][22][23][24] in which the vanishingly small magnetic flux arising from the nearly compensated magnetization is difficult to access using existing bulk magnetometry methods. In most of the previous studies, the magnetic properties of Mn 3 X films were typically inferred indirectly from magneto-transport measurements [4,5,10] or with other global measurement techniques such as neutron scattering [25] and vibrating-sample magnetometry, [6,8,21] rendering limited information on their microscopic spin configurations.…”

“…These challenges are particularly apparent for nanometer-thick Mn 3 X films, [4][5][6][7][20][21][22][23][24] in which the vanishingly small magnetic flux arising from the nearly compensated magnetization is difficult to access using existing bulk magnetometry methods. In most of the previous studies, the magnetic properties of Mn 3 X films were typically inferred indirectly from magneto-transport measurements [4,5,10] or with other global measurement techniques such as neutron scattering [25] and vibrating-sample magnetometry, [6,8,21] rendering limited information on their microscopic spin configurations. In this context, a reliable experimental approach capable of detecting Novel non-collinear antiferromagnets with spontaneous time-reversal symmetry breaking, non-trivial band topology, and unconventional transport properties have received immense research interest over the past decade due to their rich physics and enormous promise in technological applications.…”

Very-High Dynamic Range, 10,000 Frames/Second Pixel Array Detector for Electron Microscopy

“…The extension of critical performance metrics is expected to impact many types of STEM measurements. For many STEM applications, from ptychography (Chen et al, 2021) to strain (Padgett et al, 2020) and magnetic field (Xu et al, 2021) mapping, we find 128 × 128 pixels sufficient for highresolution, high precision work. As noted previously for magnetic and strain mapping, and discussed in the section on the MUIS, the ability to deliver a high dose per pixel is more important than the number of pixels on the detector (Nguyen et al, 2020).…”