On the basis of dielectric measurements performed in a wide temperature range (173–373 K), a comprehensive analysis of the dielectric and electrical properties of magnetite nanoparticles electrical conduction mechanism of compressed spherical shaped Fe₃O₄ nanoparticles was proposed. The electrical conductivity of Fe₃O₄ nanoparticles was related to two different mechanisms (correlated barrier hopping and non-overlapping small polaron tunneling mechanisms); the transition between them was smooth. Additionally, role of grains and grain boundaries with charge carrier mobility and with observed hopping mechanism was described in detail. It has been confirmed that conductivity dispersion (as a function of frequencies) is closely related to both the long-range mobility (conduction mechanism associated with grain boundaries) and to the short-range mobility (conduction mechanism associated with grains). Calculated electron mobility increases with temperature, which is related to the decreasing value of hopping energy for the tunneling of small polarons. The opposite scenario was observed for the value of electron hopping energy.

Until now, strategies used to treat cancer are imperfect, and this generates the need to search for better and safer solutions. The biggest issue is the lack of selective interaction with neoplastic cells, which is associated with occurrence of side effects and significantly reduces the effectiveness of therapies. The use of nanoparticles in cancer can counteract these problems. One of the most promising nanoparticles is magnetite. Implementation of this nanoparticle can improve various treatment methods such as hyperthermia, targeted drug delivery, cancer genotherapy, and protein therapy. In the first case, its feature makes magnetite useful in magnetic hyperthermia. Interaction of magnetite with the altered magnetic field generates heat. This process results in raised temperature only in a desired part of a patient body. In other therapies, magnetite-based nanoparticles could serve as a carrier for various types of therapeutic load. The magnetic field would direct the drug-related magnetite nanoparticles to the pathological site. Therefore, this material can be used in protein and gene therapy or drug delivery. Since the magnetite nanoparticle can be used in various types of cancer treatment, they are extensively studied. Herein, we summarize the latest finding on the applicability of the magnetite nanoparticles, also addressing the most critical problems faced by smart nanomedicine in oncological therapies.

The new (Zn,Mg,Ni,Fe,Cd)Fe₂O₄ high entropy ferrite with average crystallite size 11.8 nm was synthesized in two stages by annealing of co-precipitated amorphous precursor. The dielectric spectroscopy confirms, that the electrical conductivity and polarization processes are associated with the mobility of electrons in the structure of ferrite. It was concluded, that the both, high frequency complex dielectric permittivity as well as complex magnetic permeability are strongly temperature and frequency dependent. The AC electrical conductivity is associated with quantum mechanical tunneling of electrons and related to the transfer of charge carriers between Fe²⁺ and Fe³⁺ ions. Moreover, the microwave absorption properties were determined. The best microwave absorption properties have been confirmed in the frequency range 1.9 to 2.1 GHz for a layer which is 0.8–1 cm thick. For this range, reflection loss (RL) is lower than −25 dB and shielding effectiveness (SE) lower than −50 dB.