Spontaneous skyrmion beyond room temperature in a boron-doped CrTe

Magnetic skyrmions, vortex-like spin textures with great potential for applications in spintronics and memory devices, are typically observed in a variety of magnetic materials that include centrosymmetric and non-centrosymmetric systems [1-3]. The magnetic ground state of these materials often consists of periodic helices or stripe domains, while skyrmions are observed only in the presence of an externally applied magnetic field. Achieving skyrmion stabilization without a magnetic field is challenging and typically requires extrinsic conditions such as geometrical confinement or sweeping the magnetic field in a decreasing mode starting from the skyrmion lattice state [4,5]. Therefore, potential uses for skyrmions are currently limited by the necessity of an external magnetic field, which makes the device design more complex. Consequently, the quest for spontaneously emerging magnetic skyrmions without an external magnetic field is of utmost importance, as it holds the potential to significantly reduce the complexity of device design and eliminate the need for a magnetic field or the current source to write the memory bits. Our study, using the state-of-the-art real-space Lorentz transmission electron microscopy technique, enabled the direct observation of spontaneous skyrmions beyond room temperature in a centrosymmetric Cr_0.9B_0.1Te crystal without the presence of external magnetic fields. We delve into the role of dipole-dipole interactions in the stabilization of these zero-field skyrmions by comparing results for different sample thicknesses.

[1] S. Mühlbauer et. al., Science 323, 915 (2009).

[2] S. Parkin et. al., Science 320, 190 (2008).

[3] A. Fert et. al., Nat. Nanotechnol. 8, 152 (2013).

[4] J. Jena et. al., Sci. Adv. 6, eabc0723 (2020).

[5] J. Jena et. al., Nat. Commun. 11, 1115 (2020).