Robust skyrmion mediated reversal of ferromagnetic nanodots of 20 nm lateral dimension with high Ms and observable DMI

Abstract

Implementation of skyrmion based energy efficient and high-density data storage devices requires aggressive scaling of skyrmion size. Ferrimagnetic materials are considered to be a suitable platform for this purpose due to their low saturation magnetization (i.e. smaller stray field). However, this method of lowering the saturation magnetization and scaling the lateral size of skyrmions is only applicable where the skyrmions have a smaller lateral dimension compared to the hosting film. Here, we show by performing rigorous micromagnetic simulation that the size of skyrmions, which have lateral dimension comparable to their hosting nanodot can be scaled by increasing saturation magnetization. Also, when the lateral dimension of nanodot is reduced and thereby the skyrmion confined in it is downscaled, there remains a challenge in forming a stable skyrmion with experimentally observed Dzyaloshinskii–Moriya interaction (DMI) values since this interaction has to facilitate higher canting per spin to complete a 360° rotation along the diameter. In our study, we found that skyrmions can be formed in 20 nm lateral dimension nanodots with high saturation magnetization (1.30–1.70 MA/m) and DMI values (~ 3 mJ/m2) that have been reported to date. This result could stimulate experiments on implementation of highly dense skyrmion devices. Additionally, using this, we show that voltage controlled magnetic anisotropy based switching mediated by an intermediate skyrmion state can be achieved in the soft layer of a ferromagnetic p-MTJ of lateral dimensions 20 nm with sub 1 fJ/bit energy in the presence of room temperature thermal noise with reasonable DMI ~ 3 mJ/m2.

Skyrmion based energy-efficient straintronic physical reservoir computing

“…Such a physical RC paradigm can be well suited to learning relatively simple tasks in-situ on edge devices where energy and hardware resources are severely constrained. In future, for scaling the proposed skyrmion based reservoir, 2D magnetic materials can be used since it has been recently demonstrated that DMI increases when magnetic materials have a small thickness or monolayer as 2D magnetic materials [49], and high DMI is necessary for scaling skyrmions [23,24,50,51]. Therefore, 2D magnetic materials based straintronic PRC can be a fascinating topic to further investigate in future research.…”

“…The requirement of very small depinning current compared to domain walls in racetrack memory devices [11,[15][16][17] and their scalability have made skyrmions a potential candidate for high density and low power spintronic devices [18][19][20]. For example, our group has shown the feasibility of voltage control of skyrmions [21] and that skyrmion mediated voltage-controlled memory devices [22] can be scaled aggressively [23,24]. Similarly, skyrmion can be a viable option for low-power, small-scale reservoir devices [1,25].…”

Stabilization and racetrack application of asymmetric Néel skyrmions in hybrid nanostructures

“…In particular, the stability of skyrmions at room temperature has been demonstrated in thin films and in confined geometries, like ferromagnetic stripes and nanodots [13][14][15][16][17] . Often, in spite of the topological protection, the skyrmion configuration is not self-nucleating and is not ground state [18][19][20] . Therefore, an important question arises whether the right selection of materials and nano-structuralization or environmental conditions can improve the skyrmion stability and provide effective functionality for applications.…”

Antiferromagnetic skyrmion based shape-configured leaky-integrate-fire neuron device

“…Magnetic skyrmions have intriguing features such as inherent topological protection, nanoscale dimension (ranging from the 100 nm to the 1 nm) [19][20][21], high operating speed [21][22][23], and low-driving current density [24]. Because of these characteristics, skyrmions are the promising candidates for developing highly energy-efficient and ultra-dense integrated nanodevices.…”