5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Transitions Of Nanosized Magnetite In Glass-ceramics

Magnetite is characterized by a complex structural transition, Verwey transition at about TV = 120 K which is characterized by a sudden increase of the magnetization. When a collection of nanosized magnetite is measured in static or ac magnetic field, a superparamagnetic unblocking can also occur at temperatures TB which might overlap with the Verwey temperature. Both temperatures depend in a certain way on the nanoparticle size. We show that for magnetite obtained by crystallization of a borosilicate glass in the presence of different nucleating agents, the Verwey transition is not obscured by the unblocking process but can be totally absent in the case of very tiny magnetite nanoparticles. In addition, when the size of the nanoparticles is multimodally distributed a multimodal distribution of TB is present but not a Verwey transition.
Viorel Sandu, Victor Kuncser, Simona Greculeasa, Andrei Kuncser, Mirela Sidonia Nicolescu