Room‐Temperature Magnetic Skyrmions and Large Topological Hall Effect in Chromium Telluride Engineered by Self‐Intercalation

Abstract

physical and materials science, but also because of their great potential for energyefficient spintronic applications. [1,2] Blochtype skyrmions were first observed in B20 magnets, [3,4] where the broken inversion symmetry allows for a Dzyaloshinskii-Moriya interaction (DMI), [5,6] leading to the helical alignment of spins. Similarly, in magnetic multilayers, the broken inversion symmetry along the stacking direction also results in an interfacial DMI, stabilizing Néel-type skyrmions. [7] It has also been demonstrated that skyrmions can be created in certain ferromagnets even without significant DMI, stabilized instead by the competition among the uniaxial magnetic anisotropy, dipolar, and exchange interaction. [8][9][10][11][12][13][14][15] For future spintronic devices in which skyrmions are used as information carriers, electrical detection of skyrmions is crucial. At the adiabatic limit, itinerant spins passing through a skyrmion capture an extra Berry phase. As a result, a transverse Hall voltage will be induced in addition to the ordinary and anomalous Hall effects, known as the topological Hall effect (THE). [16] The topological Hall voltage is proportional to the topological charge (skyrmion number) Room-temperature magnetic skyrmion materials exhibiting robust topological Hall effect (THE) are crucial for novel nano-spintronic devices. However, such skyrmion-hosting materials are rare in nature. In this study, a self-intercalated transition metal dichalcogenide Cr 1+x Te 2 with a layered crystal structure that hosts room-temperature skyrmions and exhibits large THE is reported. By tuning the self-intercalate concentration, a monotonic control of Curie temperature from 169 to 333 K and a magnetic anisotropy transition from outof-plane to the in-plane configuration are achieved. Based on the intercalation engineering, room-temperature skyrmions are successfully created in Cr 1.53 Te 2 with a Curie temperature of 295 K and a relatively weak perpendicular magnetic anisotropy. Remarkably, a skyrmion-induced topological Hall resistivity as large as ≈106 nΩ cm is observed at 290 K. Moreover, a sign reversal of THE is also found at low temperatures, which can be ascribed to other topological spin textures having an opposite topological charge to that of the skyrmions. Therefore, chromium telluride can be a new paradigm of the skyrmion material family with promising prospects for future device applications.

Epitaxial van der Waals heterostructures of Cr2Te3 on 2D materials

“…Skyrmions nucleate during the magnetization reversal and give rise to an extra transverse transport channel inducing a peak in the Hall resistivity. Imaging such spin textures has been performed by Lorentz-TEM in Cr 3 Te 4 layers [46]. Nevertheless, another explanation has been put forward by other groups as two anomalous Hall contributions with opposite signs [47].…”

Tailing the Magnetoelectric Properties of Cr2Ge2Te6 by Engineering Covalently Bonded Cr Self-Intercalation: Ferromagnetic Half-Metal

“…In 2022, the phase-selective synthesis of trigonal and monoclinic Cr 5 Te 8 crystals was achieved, using chemical vapor deposition . The successful experimental SI realization in 2D materials paves a new way to modulate the magnetoelectric properties of 2D materials. ,,,, …”

“…53 The successful experimental SI realization in 2D materials 54 paves a new way to modulate the magnetoelectric properties of 2D materials. 50,51,53,55,56 In this article, by using the first-principles method, we perform a systematic research on the magnetic and electronic properties of SI-CGT bilayers and multilayers. The SI-CGT bilayers are HMs with interlayer FM order, independent of stacking patterns and Cr SI atoms' concentration.…”

Extreme Air Sensitivity and Nonself-Limited Oxidation of Two-Dimensional Magnetic Tellurides

“…21 Beyond robust ferromagnetism, many Cr 1+δ Te 2 compounds and their heterostructures have shown signatures of magnetic skyrmions up to room temperature as evidenced by the topological Hall effect (THE) 43−48 and direct visualization via Lorentz transmission electron microscopy (TEM). 17,49,50 The realization of room temperature skyrmions may pave the way toward the development of vdW-integrated racetrack memory devices for next-generation information technology.…”

“…Very recently, chromium tellurides (Cr 1+δ Te 2 ) have emerged as a promising family of self-intercalated vdW magnets which possess considerable potential to address the above challenges. − CrTe 2 (without Cr intercalants) has been reported to host long-range ferromagnetic order up to ∼310 K. , The magnetic properties of the system can be effectively tuned by the intercalation of Cr in the vdW gap, by the reduction of thickness down to the 2D limit, ,, and by the creation of twisted vdW superstructures . Beyond robust ferromagnetism, many Cr 1+δ Te 2 compounds and their heterostructures have shown signatures of magnetic skyrmions up to room temperature as evidenced by the topological Hall effect (THE) − and direct visualization via Lorentz transmission electron microscopy (TEM). ,, The realization of room temperature skyrmions may pave the way toward the development of vdW-integrated racetrack memory devices for next-generation information technology.…”