Pyroelectric detection of spontaneous polarization in magnetite thin films

Abstract

We have investigated the spontaneous polarization in Fe${}_3$O${}_4$ thin films by using dynamic and static pyroelectric measurements. The magnetic and dielectric behavior of Fe${}_3$O${}_4$ thin films grown on Nb:SrTiO${}_3$(001) substrates was consistent with bulk crystals. The well-known metal-insulator (Verwey) transition was observed at 120 K. The appearance of a pyroelectric response in the Fe${}_3$O${}_4$ thin films just below the Verwey temperature shows that spontaneous polarization appeared in Fe${}_3$O${}_4$ at the charge ordering transition temperature. The polar state characteristics are consistent with bond- and site- centered charge ordering of Fe${}^{2+}$ and Fe${}^{3+}$ ions sharing the octahedral $B$ sites. The pyroelectric response in Fe${}_3$O${}_4$ thin films was dependent on the dielectric constant. Quasi-static pyroelectric measurement of Pd/Fe${}_3$O${}_4$/Nb:SrTiO${}_3$ junctions showed that magnetite has a very large pyroelectric coefficient of 735 nC/cm${}^2$K at 60 K.

arXiv comment8 pages, 8 figures

References in corpus (6)

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• Spintronic oxides grown by laser-MBE
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