  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.
