Para process in the ferrite MnFe$_2$O$_4$ at low temperatures

It is shown that, in the ferrite MnFeO$_4$ below 240 K, the para process (increase in the true magnetization in strong magnetic fields) is associated with de localization of electrons in the covalent bonds $Mn_{B}^{2+}-Mn_{B}^{2+}$ and $Fe_{B}^{3+}-Fe_{B}^{3+}$. An external magnetic field compressing the 3d shell of the cations breaks the covalent bonds, which leads to disruption of spin pairing in these bonds, and hence to increase in magnetic moment of the cations Mn$_{B}^{2+}$ and Fe$_{B}^{3+}$ in an octahedral sublattice, which is responsible for the magnetic moment in Mn ferrite. It is suggested that the underestimated experimental value of the magnetic moment $n_0$ at the absolute zero in Mn ferrite is basically due to spin pairing of the electrons localized at covalent bonds between cations B.