Evidence of random magnetic anisotropy in ferrihydrite nanoparticles based on analysis of statistical distributions

TL;DR

This study demonstrates that the magnetic anisotropy energy in ferrihydrite nanoparticles scales with the square root of their volume, indicating the presence of random local anisotropy consistent with a homogeneous structure.

Contribution

The paper introduces a statistical distribution analysis method to reveal the random anisotropy behavior in ferrihydrite nanoparticles, linking it to their homogeneous structure.

Findings

Anisotropy energy scales with the square root of nanoparticle volume.

Distribution analysis confirms random local anisotropy.

Ferrihydrite has a homogeneous single-phase structure.

Abstract

We show that the magnetic anisotropy energy of antiferromagnetic ferrihydrite depends on the square root of the nanoparticles volume, using a method based on the analysis of statistical distributions. The size distribution was obtained by transmission electron microscopy, and the anisotropy energy distributions were obtained from ac magnetic susceptibility and magnetic relaxation. The square root dependence corresponds to random local anisotropy, whose average is given by its variance, and can be understood in terms of the recently proposed single phase homogeneous structure of ferrihydrite.