Localized ferromagnetic resonance in inhomogeneous thin films

Area of Science:

• Condensed matter physics
• Materials science

Background:

• Ferromagnetic resonance (FMR) is a key technique for probing magnetic properties.
• Understanding linewidth variations is crucial for magnetic thin film applications.
• Sample inhomogeneity is a known factor affecting FMR linewidth.

Purpose of the Study:

• To theoretically investigate the influence of sample inhomogeneity on FMR linewidth in ferromagnetic thin films.
• To develop a model accounting for inhomogeneities across various length scales.

Main Methods:

• Diagonalization of a spin wave Hamiltonian was employed.
• A model incorporating size D grains with random anisotropy fields H(p) was utilized.
• Analysis considered film thickness d and magnetization M(s).

Main Results:

• The model accurately predicts linewidth for small inhomogeneities (H(p)D << piM(s)d), aligning with the two-magnon model.
• For large inhomogeneities (H(p)D >> piM(s)d), magnetic precession localizes.
• The spectrum transitions towards local precession on individual grains.

Conclusions:

• Sample inhomogeneity fundamentally alters ferromagnetic resonance linewidth behavior.
• The developed model provides a framework for understanding linewidth dependence on inhomogeneity scale.
• Results have implications for designing and characterizing magnetic thin film devices.