Study of reorientation processes in L1₀-ordered FePt thin films.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Epitaxially grown L1₀ FePt thin films are crucial for magnetic storage applications.
• Understanding the development of structural and magnetic order during annealing is key to optimizing film properties.

Purpose of the Study:

• To investigate the evolution of magnetic anisotropy and domain structure in L1₀ FePt thin films during annealing.
• To model the kinetics of magnetic domain reorientation using an adapted Johnson-Mehl-Avrami approach.

Main Methods:

• Conversion electron Mössbauer spectroscopy (CEMS) to study magnetic order.
• Monte Carlo simulations to corroborate experimental findings.
• Application of a modified Johnson-Mehl-Avrami (JMA) model to analyze annealing kinetics.

Main Results:

• Annealing induces a transition of the easy magnetization axis from out-of-plane to in-plane.
• Domain reorientation shows an initial increase followed by a decrease before saturation.
• The annealing process is characterized by two distinct dynamical processes: initial 2D-growth and later 3D-growth.

Conclusions:

• The study successfully describes the complex domain reorientation dynamics in FePt films using a modified JMA model.
• Activation energies for disordering (1.5(1) eV) and ordering (0.8(2) eV) were determined, providing insights into the underlying atomic mechanisms.