Thermoinduced magnetization and uncompensated spins in antiferromagnetic nanoparticles

We have investigated the combined effect of an uncompensated moment and the thermoinduced magnetization on the initial susceptibility of nanoparticles of antiferromagnetic materials. We find that for nanoparticles with small values of the anisotropy and exchange fields, the thermoinduced magnetization may be predominant at finite temperatures. In other cases the uncompensated moment may be predominant.

Figure 1

Coordinate system used in the calculations. The differences in angles and lengths are exaggerated.

Figure 2

$\mid {\omega }_{\pm }∕\gamma \mid$ as a function of $\xi$, calculated using Eq. (7), with $B_{\mathrm{app}}=0\mathrm{T}$, $B_{\mathrm{a}}=0.01\mathrm{T}$, and $B_{\mathrm{E}}=300\mathrm{T}$. Full line: $-$ mode, dashed line: $+$ mode.

Figure 3

(Color online) Simulated ${\chi }_i$ vs temperature curves, with $V={10}^{-24}{\mathrm{m}}^3$, $B_a=0.01\mathrm{T}$, $B_E=300\mathrm{T}$, and ${\mu }_u=\left(\mathrm{a}\right)$ $50{\mu }_B$, $\left(\mathrm{b}\right)$ $100{\mu }_B$, and $\left(\mathrm{c}\right)$ $200{\mu }_B$. The dashed line shows the total susceptibility, the increasing full line shows the thermoinduced contribution, while the decreasing full line shows the contribution from the uncompensated spins.