A deep insight into the magnetic properties of cobalt ferrite by non-equilibrium thermodynamics with internal variables

The paper presents for the first time an in-depth theoretical magnetic characterization of cobalt ferrite nano- particles (CoFe2O4) by using the thermodynamic approach of non-equilibrium with internal variables. Consid- ering that a complete knowledge of the structure and properties is crucial to design a material for a specific application, a complete thermodynamic characterization of magnetic properties turns out to be useful for a plethora of technological and biomedical purposes. The non-equilibrium thermodynamics is exploited to calculate the internal variables as a function of the perturbation frequencies. Our results allow to fully characterizing the investigated material in terms of magnetization by orientation and by deformation (M(1) and M(0)), magnetic field B(1), magnetization displace- ment current (E), entropy production (σ), phenomenological coefficients (L(0,0) and L(1,1)) and state coefficients (a(0,0), a(1,1)). CoFe2O4 has been selected as a proof of concept; our theoretical investigation and parameters are applicable to all the para- and ferromagnetic materials, including biomolecules and biological tissues allowing to compare healthy and pathological behavior, subjected to a variable magnetic field for which it is possible to conceive a linear approximation.