Microscopic Study of the AC Conductivity in MgFe2O4. Appearance of the Magnetic Polaron

A microscopic study of the large or dielectric polaron behaviour has been carried out for the first time for MgFe₂O₄. We have considered a new methodology to study in depth the Overlap Large Polaron Tunneling (OLPT) conduction mechanism in a large temperature range. This methodology consists in extracting theory from experimental data. Unexpected and even spectacular results are determined. However, to the best of our knowledge, it is for the first time, that we prove the existence of the magnetic polaron in MgFe₂O₄ in the ferromagnetic phase as an alternative to the dielectric one. The function added to the trapping potential shows a competitive behavior between the magnetic effect and the crystal lattice acoustic vibration. Our theoretical model can be generalized for ferrite materials exhibiting the (OLPT) conduction mechanism. Indeed, this model allows checking the existence or not of the magnetic polaron, to determine its radius, the magnetic correlation length variation with frequency, the formation temperature of the magnetic polaron (T_M) and other features sometimes inaccessible even experimentally.

Graphical Abstract