/Atomistic modeling of magnetism dynamics for highly scaled spin-logic devices

Atomistic modeling of magnetism dynamics for highly scaled spin-logic devices

PhD - Leuven | More than two weeks ago

Towards an atomistic description of magnetic switching and domain propagation in highly scaled materials and devices using time-resolved magnetic Monte-Carlo.

The dynamics of magnetization plays an important role in the scaled magnetic memory (MRAM) and spin logic devices being investigated at imec. A particularly interesting problem is the coupling of the magnetic and electrical domains, where ferroelectric and magnetoelectric effects at interfaces are explored. Historically, spin- transport and magnetism dynamics in these systems have been modelled using effective (e.g., semi-classical, phenomenological, mean-field) models. Investigations into the magnetic order in layered semiconducting materials such as CrI3, CrGeTe3, VSe2, have already demonstrated the limitations of these effective models [1]. For nano-scaled spin-logic devices, using thin film magnetic materials and exploiting interfacial magnetization dynamics, atomistic effects will become increasingly important and more rigorous modelling is required.

The Ph.D. candidate will build on our recent work for modelling the phase transition and spin-dynamics of layered magnets from first principles [1-2]. This approach goes beyond the typically used phenomenological Landau-Lifshitz-Gilbert (LLG) description and use an atomistic time-quantified Monte Carlo (TQMC) approach. Parameters for this model are obtained from first-principles density functional theory (DFT) calculations. To describe spin wave transport, the candidate will extend the existing TQMC code to the low damping regime using a Fokker-Planck approach. To describe the electrical generation and detection of magnetization, models accounting spin transfer torque (STT), spin-orbit torque (SOT), and the Dzyaloshinskii-Moriya interaction (DMI) will be added where necessary. To account for the damping of the magnetic precession, intrinsic, extrinsic and interfacial relaxation effects will be considered.

With the TQMC code, the candidate will study future spin-logic devices in strong collaboration with the exploratory experimental research at imec. These applications will influence the models that need to be introduced in the code. Armed with an increased understanding of magnetization dynamics, the candidate will focus on the design and optimization of key components of spin-logic such as transducers and waveguides. In addition, a comparison to the standard LLG approach will provide a better understanding of its limitations in scaled non-ideal structures with domain boundaries and interfaces and lead to an improvement in these effective models.

 

[1] S. Tiwari, M. L. Van de Put, B. Sorée, and W. G. Vandenberghe, “Critical behavior of ferromagnets CrI3, CrBr3, CrGeTe3, and anti-ferromagnet FeCl2: a detailed first-principles study," Phys. Rev. B 103, 014432 (2021)

[2] S. Tiwari, M. L. Van de Put, K. Temst, W. G. Vandenberghe, and B. Sorée, “Atomistic modeling of spin and electron dynamics in two-dimensional magnets switched by two-dimensional topological insulators”, Phys. Rev. Applied, under review (2022)



Required background: Solid State Physics, Material Science, Electrical Engineering.

Type of work: 20% literature, 50% modeling and implementation, 30% simulation and design

Supervisor: Bart Soree

Daily advisor: Maarten Van de Put

The reference code for this position is 2023-022. Mention this reference code on your application form.

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