Tunable Magnetization Dynamics in Interfacially Modified Ni81Fe19/Pt Bilayer Thin Film Microstructures.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Ultrafast magnetic properties are crucial for high-speed magnetic devices.
• Controlling magnetization dynamics at interfaces is a key challenge.
• Focused ion beam (FIB) irradiation offers a method for nanoscale material modification.

Purpose of the Study:

• To investigate the effect of low-dose FIB irradiation on the ultrafast magnetic properties of Ni81Fe19/Pt bilayers.
• To understand the relationship between FIB dose and magnetization dynamics, including damping and precession.
• To explore the potential of FIB for tailoring magnetic properties for device applications.

Main Methods:

• Fabrication of Ni81Fe19/Pt bilayers.
• Low-dose focused ion beam irradiation with varying doses (0 to 3.3 pC/μm²).
• All-optical time-resolved magneto-optical Kerr microscopy (TR-MOKE) for studying magnetization dynamics (relaxation, precession, damping, spatial coherence).
• Analysis of magnetization precession using single-mode damped sinusoid fitting to extract the Gilbert damping parameter.

Main Results:

• Demonstrated interface modification of ultrafast magnetic properties via low-dose FIB irradiation.
• Observed a complex dependence of the Gilbert damping parameter and precession frequency on FIB irradiation dose.
• Interpreted the observed effects in terms of intrinsic changes and extrinsic two-magnon scattering due to interfacial alloying and expansion.

Conclusions:

• Low-dose FIB irradiation provides a novel method for controlling ultrafast magnetic properties at interfaces.
• The complex dose-dependent behavior suggests a combination of intrinsic and extrinsic scattering mechanisms.
• This approach opens opportunities for optimizing precessional magnetization dynamics in high-speed magnetic devices.