Magnetocrystalline Anisotropy Energy Simulations for R&D of Magnetic Materials

QuantumATK Team together with scientists from SPEC CEA, Universite Paris Saclay, as part of the EU COSMICS research project, published a paper on the simulation of magnetocrystalline anisotropy energy (MAE) of Fe, Co and Ni slabs [1]. This work shows that simulations with QuantumATK can be efficiently used to investigate the parameters controlling the MAE, such as thickness and crystallographic orientations of these materials as bulk, slabs, surfaces or interfaces. As tunability of MAE is often a desired functionality of magnetic materials, modeling is an important part of the R&D workflow for designing materials with optimized magnetic properties. For example, novel emerging memory architectures such as magnetic random-access memories (MRAM) rely on materials with optimized MAE properties to store and retain information. Larger MAE provides good retention characteristics of a given magnetic state, i.e, store the magnetization direction for a certain time, whereas lower MAE is required to switch the magnetization direction at will during the binary writing process.

Figure 1. (a) Evolution of the MAE for Co with the slab thicknesses ranging from 1 to 15 layers and different crystallographic orientations [1]. Whereas for very small thicknesses large MAE values as well as large amplitudes of oscillations are observed, for thicker slabs MAE generally stabilizes. This can be explained by examining site resolved MAE for the 15-layer Co system (b). Whereas largest perturbations are observed for two or three surface layers, sublayers nearly counterbalancing the outermost layers, only small oscillations are observed for the central part, converging to the bulk value.

Key advantages of MAE simulations with QuantumATK

  • QuantumATK is the only code including pseudopotential-based density-functional theory (DFT) methods with LCAO and plane-wave basis sets in one framework. This makes it possible to shift seamlessly from LCAO to plane-wave basis sets, thus, easily adjust and test tradeoffs between speed and accuracy of the MAE simulations, and finally perform simulations of bigger systems with LCAO basis sets.

 

  • MAE calculations, i.e. energy differences for different magnetization orientations, are numerically delicate. In order to provide accurate results, QuantumATK comes with good default values for the numerical parameters, such as k-point sampling and bands per electron, and possibility to easily tune them. Furthermore, QuantumATK provides efficient numerical methods to decompose MAE as a sum of local contributions in heterogeneous systems, such as surfaces, interfaces, or any type of defects.

 

  • QuantumATK provides advanced graphical user interface (GUI) for both setting up and analyzing the results, as shown in Figure 2 and Figure 3. Advanced restart functionality makes users more efficient in performing MAE simulations, as it enables rerunning MAE simulations without recalculating any previous data and easily including new magnetization orientations and projections.

Figure 2 Set up MAE simulations using NanoLab GUI. Specify magnetization orientations, projections (sites, sites and shells, sites and orbitals), energy window and numerical parameters.

Figure 3 Analyze MAE results using NanoLab GUI Plot MAE as a function of the chosen coordinate at available magnetization orientations, site/shell/orbital-projected MAE. Combine configuration and MAE plots.

Additional Information

Other resources

Manual on calculating Magnetic Anisotropy Energy with QuantumATK

References

[1] L. Le Laurent, C. Barreteau, and T. Markussen, “Magnetocrystalline anisotropy of Fe, Co, and Ni slabs from density functional theory and tight-binding models”, Phys. Rev. B 100, 174426 (2019). arXiv: 1907.04532

QuantumATK reference paper is now available

Check out our recently published reference paper “QuantumATK: an integrated platform of electronic and atomic-scale modelling tools”  [1]  which gives  a general overview of the entire QuantumATK platform.

[1] S. Smidstrup, T. Markussen, P. Vancraeyveld, J. Wellendorf, J. Schneider, T. Gunst, B. Vershichel, D. Stradi, P. A. Khomyakov, U. G. Vej-Hansen, M.-E. Lee, S. T. Chill, F. Rasmussen, G. Penazzi, F. Corsetti, A. Ojanpera, K. Jensen, M. L. N. Palsgaard, U. Martinez, A. Blom, M. Brandbyge, and K. Stokbro, “QuantumATK: An integrated platform of electronic and atomic-scale modelling tools”, J. Phys.: Condens. Matter 32, 015901 (2020). arXiv: 1905.02794v2.

Learn more about QuantumATK products

Interested in applying QuantumATK software to your research? Test our software or contact us at quantumatk@synopsys.com to get more information on QuantumATK platform for atomic-scale modeling.