Invited Lecture

Gil Markovich Amir Hevroni
School of Chemistry, Tel Aviv University, Tel Aviv, Israel

Magnetite (Fe3O4) nanocrystals have very interesting electronic properties. These properties were explored in two types of variable temperature STM experiments. In the first one, the high spin-polarized conductance of magnetite was used to measure the magnetization switching dynamics using a spin-filtering substrate and by tuning the temperature close to the magnetization blocking temperature of the nanocrystals. The temporal analysis of the magnetization switching events enabled us to extract various parameters relating to the nanocrystals. In the second experiment, the current/voltage characteristics measured as a function of temperature over selected single magnetite nanocrystals revealed a sharp jump in the density of states and bandgap magnitude at about 100K, which is a manifestation of the well-known Verwey metal-insulator transition, studied in bulk magnetite crystals since 1939. The nanocrystal experiments reveal new information regarding the existence of this transition in such small systems.

Double barrier tunnel junction configuration used for tunneling spectroscopy in the second experiment for detecting the Verwey transition

Sample configurations for the two types of experiments mentioned above.

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