Galvanomagnetic properties of fast neutron bombarded Fe3O4 magnetite: A case against charge ordering mechanism of the Verwey transition

Synthetic single-crystalline samples of Fe3O4 magnetite were subjected to fast neutron bombardment with a fluency Φ=2.2×1020 cm−2. A comparative study of the electrical resistivity ρ, normal (ordinary) and anomalous (extraordinary) Hall effects, and the magnetoresistance in a temperature range from 50 to 400 K (i.e across the Verwey transition (VT) at T V ∼ 125 K) was performed on both as grown and irradiated samples. The galvanomagnetic properties were investigated in magnetic fields B up to 13.6 T. From the normal (ordinary) Hall effect the concentration of charge carriers was determined. The activation energy was also estimated. On the Verwey transition the conductivity type was changed form electronic to hole. Contrary to expectations, the fast neutron irradiation resulted only in a minor decrease in T V by ∼4 K. The results gathered evidence against a distributed opinion that the charge ordering on the octahedral sites in the spinel structure of Fe3O4 is a major driving factor of the Verwey transition.