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arXiv · 2204.03092

Size effects in the Verwey transition of nanometer-thick micron-wide magnetite crystals

Adolfo del Campo·Sandra Ruiz-Gómez·Eva M. Trapero·Cecilia Granados-Miralles·Adrián Quesada·Michael Foerster·Lucía Aballe·José Emilio Prieto·Juan de la Figuera
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Abstract

We have monitored the Verwey transition in micrometer-wide, nanometer-thick magnetite islands on epitaxial Ru films on Al2O3(0001) using Raman spectroscopy. The islands have been grown by high-temperature oxygen-assisted molecular beam epitaxy. Below 100 K and for thicknesses above 20 nm the Raman spectra correspond to those observed in bulk crystals and high quality thin films for the sub-Verwey magnetite structure. At room temperature the width of the cubic phase modes is similar to the best reported in bulk crystals, indicating a similar level of electron-phonon interaction. The evolution of the Raman spectra upon cooling suggests that for islands thicker than 20 nm, structural changes appear first at temperatures starting at 150 K and the Verwey transition itself takes place at around 115 K. However, islands thinner than 20 nm show a very different Raman spectra indicating that while a transition takes place, the charge order of the ultrathin islands differs markedly from their thicker counterparts

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Adolfo del Campo, Sandra Ruiz-Gómez, Eva M. Trapero, Cecilia Granados-Miralles, Adrián Quesada, Michael Foerster, Lucía Aballe, José Emilio Prieto, Juan de la Figuera. 2022-04-06. Size effects in the Verwey transition of nanometer-thick micron-wide magnetite crystals. https://doi.org/10.1021/acs.jpcc.2c03391

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