Magnetotransport studies of Fe vacancy-ordered Fe4+δSe5 nanowires
The strong frequency dependence of the resistive transition in the magnetite Fe3O4 nanowire is closely associated with the well-known Verwey transition. The Fe vacancy-ordered Fe4+δSe5 shows the presence of the 1:1 ratio of Fe2+/Fe3+ mixed-valence state, which is similar to that found in Fe3O4. The recent magnetotransport study on Fe4+δSe5 nanowire shows a metal-insulator (MI) transition at about 30 K in the absence of magnetic fields, and the transition temperature is strongly enhanced by magnetic-field. The angular-dependent magnetoresistance measurements show that the transport behavior changes from two-dimensional to one-dimensional-like at temperatures much lower than the transition temperature. A strong AC-excitation frequency dependence of the resistive transition observed in this material provides additional evidence for the Verwey-like electronic correlation. This is the first time a non-oxide compound to show the Verwey-like transition, suggesting an orbital or charge order in this material. This work was carried by the group led by Prof. Maw-Kuen Wu, and the results were published in the 2020 May 20 issue (online) of the Proceedings of National Academy of Sciences of the U.S.A.
Figure: (a) TEM image and (b) the corresponding SAED pattern of the Fe4+δSe5 nanowire exhibiting the √5×√5 Fe-vacancy order. (c) The frequency-dependent resistive transition of the nanowire. The inset shows the frequency dependence for TMI, and To.
