Dynamic Skyrmion-Mediated Switching of Perpendicular MTJs: Scaling to 20 nm with Thermal Noise*

One method of creating and annihilating skyrmions in confined geometries is to use Voltage-Controlled Magnetic Anisotropy (VCMA) [1, 2, 3]. Previous study shows that robust voltage controlled ferromagnetic reversal from “up” to “down” state in the soft layer of a p-MTJ can be achieved by creating and subsequently annihilating an intermediate skyrmion state [4] in the presence of room temperature thermal noise and anisotropy variation across grains [4]. However, when scaling to 20 nm, thermal noise can annihilate the skyrmions, for example, by randomly moving the core towards the boundary of the nanostructure. Thus, a region of different anisotropy in the skyrmion core may be needed to stabilize the skyrmion state allowing competitive scaling. Here, we will investigate the extent to which the skyrmion mediated switching scheme can scale to lateral dimensions ~ 20 nm in ferromagnets.

References:
[1] Y. Nakatani, et al., Appl. Phys. Lett., 108, 152403 (2016).
[2] D. Bhattacharya, et al., Scientific Reports, 6, 31272 (2016).
[3] D. Bhattacharya, et al., arXiv,1904.00701(2019).
[4] D. Bhattacharya and J. Atulasimha, ACS Appl. Mater. Interfaces, 10, 20, 17455 (2018).