New simulations use disorder to more accurately depict platinum-cobalt thin film interactions

Because of their stability, ease of manipulation and nanoscale size, pointlike regions of reversed magnetization, called magnetic skyrmions, have attracted attention for storing, transporting and manipulating information. One key driver in stabilizing these quasiparticles is the Dzyaloshinskii-Moriya interaction, which contributes to the alignment of magnetic moments with respect to each other. New work is attempting to simulate DMIs closer to what is observed experimentally.

Zimmermann et al. have calculated the DMI in the presence of disorder to improve the accuracy of such simulations as they occur at interfaces between platinum and cobalt thin films. In an international collaboration between Forschungszentrum Jülich and CNRS/Thales joint laboratory in Palaiseau, the team used the coherent potential approximation to simulate intermixing of Co and Pt atoms as well as the introduction of several other chemical elements as third components.

“In contrast to other typical magnetic interactions, [which] align the moments in a collinear fashion, the DMI is responsible for a twisting of the moments,” said Bernd Zimmermann, lead author of the paper. “This leads to a plethora of intriguing effects, from chiral domain walls via nonreciprocal spin-waves to topological magnetic states such as skyrmions.”

Simulated systems were found to be robust against the degree of intermixing, which agrees with the experimental literature on the subject.

When a third element is introduced, the systems are predicted to exhibit DMI reductions, a finding that the authors state opens possibilities for such technology to be tunable.

Zimmermann said the authors hope that their work will lead to further experimental efforts to quantify intermixing as well as expand to other heterostructures and types of disorder.

Source: “Dzyaloshinskii-Moriya interaction at disordered interfaces from ab initio theory: Robustness against intermixing and tunability through dusting,” by Bernd Zimmermann, William Legrand, Davide Maccariello, Nicolas Reyren, Vincent Cros, Stefan Blügel, and Albert Fert, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5049876 .