Temperature dependence of antiferromagnetic susceptibility in ferritin

TL;DR

This study reveals that antiferromagnetic susceptibility in ferritin increases with temperature at high magnetic fields, aligning with bulk antiferromagnet behavior, contrasting previous low-field findings due to insufficient field saturation.

Contribution

It demonstrates the temperature dependence of ferritin's antiferromagnetic susceptibility at high fields, clarifying previous contradictory results caused by limited field range.

Findings

Susceptibility increases with temperature at high fields

Behavior aligns with bulk antiferromagnets and superantiferromagnetism models

Contrasts previous low-field results due to saturation issues

Abstract

We show that antiferromagnetic susceptibility in ferritin increases with temperature between 4.2 K and 180 K (i. e. below the N\'{e}el temperature) when taken as the derivative of the magnetization at high fields ($30\times10^4$ Oe). This behavior contrasts with the decrease in temperature previously found, where the susceptibility was determined at lower fields ($5\times10^4$ Oe). At high fields (up to $50 \times10^4$ Oe) the temperature dependence of the antiferromagnetic susceptibility in ferritin nanoparticles approaches the normal behavior of bulk antiferromagnets and nanoparticles considering superantiferromagnetism, this latter leading to a better agreement at high field and low temperature. The contrast with the previous results is due to the insufficient field range used ($< 5 \times10^4$ Oe), not enough to saturate the ferritin uncompensated moment.