Correlation, excitation, and relaxation of the antiferromagnetic nanoparticle

TL;DR

This paper investigates the spin dynamics in hematite nanoparticles, revealing how antiferromagnetic exchange influences relaxation processes and aligns with experimental observations.

Contribution

It introduces a semi-quantitative analysis of exchange effects on spin relaxation in antiferromagnetic nanoparticles, integrating theoretical modeling with experimental data.

Findings

Exchange $J$ reduces superparamagnetic relaxation

Incoherent relaxation of transverse spins at low temperature

Theoretical results agree with inelastic neutron scattering data

Abstract

We study the dynamics of spins in the canted antiferromagnetic hematite nanoparticles $\alpha$-Fe$_2$O$_3$. The system includes an antiferromagnetic exchange ($J$) between two sublattices as well as the potential dominated by a uniaxial anisotropy and dissipates through the thermally triggered spin-phonon mechanism. The exchange $J$ is found to reduce the superparamagnetic relaxation and drive the incoherent relaxation of transverse spins in the low temperature. Dynamical properties are semi-quantitatively understood within a role of the exchange interaction $J$ and agree well with recent inelastic neutron scattering experiments.