Dynamical diffraction simulations in FePt--I.

Area of Science:

• Materials Science
• Solid State Physics
• Electron Microscopy

Background:

• Electron diffraction is vital for characterizing crystalline materials.
• Accurate simulations are needed to interpret complex diffraction patterns.
• L1₀ FePt is a technologically important magnetic material.

Purpose of the Study:

• To quantify the influence of order, composition, and thickness on electron diffraction intensities in L1₀ FePt.
• To address simulation challenges arising from L1₀ symmetry and tetragonality.
• To develop a hybrid atom model for accurate simulations of non-equiatomic compositions.

Main Methods:

• Performed multislice simulations for dynamical diffraction studies.
• Utilized both convergent electron beam diffraction (CBD) and selected area electron diffraction (SAED) conditions.
• Developed a hybrid weighting function atom for Fe-Pt to handle varying compositions and order parameters.

Main Results:

• Simulations revealed significant differences in intensity ratios for films with varying compositions but similar unit cell numbers and order.
• Addressed simulation complexities related to the {111} plane normal and <111> direction due to tetragonality.
• The hybrid atom approach simplified the construction of complex crystal structures for simulation.

Conclusions:

• Electron diffraction intensities are highly sensitive to subtle changes in material order, composition, and thickness.
• Accurate multislice simulations, accounting for material specifics like tetragonality, are essential for reliable interpretation.
• The developed simulation methodology provides a robust framework for studying ordered intermetallic compounds.