Coercivity of homogenized ensembles of anisotropic $\gamma$-Fe$_2$O$_3$ nanoparticles

The influence of interaction between anisotropic $\gamma$-Fe$_2$O$_3$ nanoparticles on their coercive force $H_c$ is studied. In samples where the degree of homogenization of anisotropic $\gamma$-Fe$_2$O$_3$ nanoparticles is high owing to mechanical, ultrasonic, and magnetic dispersion with subsequent filtering of resulting suspensions, $H_c$ is almost independent of volume concentration $\eta$ of the particles when $\eta$ varies between 4$\times$10$^{-4}$ and 10$^{-1}$. In samples homogenized only mechanically, the $H_c$ versus $\log\eta$ dependence is linear.