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Molecular Auxetic Behavior of Epitaxial Co-Ferrite Spinel Thin Film

Authors

  • Matjaz Valant,

    Corresponding author
    1. Materials Research Laboratory University of Nova Gorica 5000 Nova Gorica (Slovenia)
    2. Department of Materials Imperial College London South Kensington Campus London SW7 2AX (United Kingdom)
    • Materials Research Laboratory University of Nova Gorica 5000 Nova Gorica (Slovenia).
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  • Anna-Karin Axelsson,

    1. Department of Materials Imperial College London South Kensington Campus London SW7 2AX (United Kingdom)
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  • Frederic Aguesse,

    1. Department of Materials Imperial College London South Kensington Campus London SW7 2AX (United Kingdom)
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  • Neil M. Alford

    1. Department of Materials Imperial College London South Kensington Campus London SW7 2AX (United Kingdom)
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Abstract

In functional oxide materials so-called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of −0.85. A hinge-like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano-devices.

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