Spontaneous Small Biskyrmions in a Centrosymmetric Rare-Earth Kagome Ferrimagnet

Abstract

Magnetic skyrmions with nontrivial topologies have great potential to serve as memory cells in novel spintronic devices. Small skyrmions were theoretically and experimentally confirmed to be generated under the influence of external fields in ferrimagnetic films via Dzyaloshinskii–Moriya interactions (DMIs). However, this topological state has yet to be verified in ferrimagnetic crystals, especially in the absence of external fields and DMIs. Here, spontaneous biskyrmions were directly observed in the Tb0.2Gd0.8Co2 ferrimagnetic crystal with a Kagome lattice using Lorentz transmission electron microscopy. The high-density biskyrmions exhibited a small size (approximately 50 nm) over a wide temperature range, were closely related to subtle magnetic interaction competition, and coexisted with some broken stripes that could be easily converted into zero-field biskyrmions by utilizing proper field-cooling manipulation. These results can be used to establish a platform for investigating functional sub-50-nm skyrmions in ferrimagnetic crystals and to facilitate advanced applications in magnetic devices. Scientists have found a new method to control small skyrmions, which are tiny magnetic patterns, in ferrimagnetic materials (materials that have a net magnetic moment even without an external magnetic field arising from the two opposite magnetic sublattices). The research, led by S.L. Zuo and K.M. Qiao, revealed that these skyrmions can be maintained in ferrimagnetic materials without requiring an external magnetic field. The researchers used a technique called Lorentz transmission electron microscopy to observe the skyrmions in a specific ferrimagnetic crystal, Tb0.2Gd0.8Co2. They discovered that the skyrmions remained stable across a broad temperature range and could be easily controlled by altering the temperature or applying a minor magnetic field. This finding could be crucial for the creation of future spintronic devices, devices that use the rotation of electrons to store and process data. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.