Thermal expansion of magnetite (4.2–300 K)

Abstract

The thermal expansion of a synthetic single-crystal sample of magnetite (Fe₃O₄) in the [111] direction has been investigated for the temperature range of 4.2–300 K using three-terminal capacitance dilatometry. The strain results and corresponding thermal expansion curve show the Verwey transition to be first-order with T _v = 120 ± 2 K. At T = 4.2–70 K, the sample shows Invar-like behaviour.

Keywords:

• magnetite
• Verwey transition
• three-terminal capacitance dilatometry
• thermal expansion

Acknowledgements

We would like to thank Dr Andrew Prentice (Monash University) for his original request for a number for the low-temperature expansion coefficient for magnetite, which gave rise to this project, and to acknowledge Dr Henry Pinto (HUT) and Dr Guy White (formerly of CSIRO) for helpful discussions.