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The Poisson Ratio in CoFe 2 O 4 Spinel Thin Films
Author(s) -
Foerster Michael,
Iliev Milko,
Dix Nico,
Martí Xavier,
Barchuk Mykhailo,
Sánchez Florencio,
Fontcuberta Josep
Publication year - 2012
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201200257
Subject(s) - materials science , auxetics , poisson's ratio , raman spectroscopy , spinel , thin film , poisson distribution , diffraction , substrate (aquarium) , ab initio , condensed matter physics , crystallography , analytical chemistry (journal) , composite material , nanotechnology , optics , metallurgy , chromatography , statistics , physics , mathematics , oceanography , chemistry , quantum mechanics , geology
The response of epitaxial CoFe 2 O 4 thin films to biaxial compressive stress imposed by MgAl 2 O 4 and SrTiO 3 single crystalline substrates is studied using X‐ray diffraction and Raman spectroscopy. It is found that the Poisson ratio ν signals a non‐auxetic behavior and depends on the substrate used. The Raman modes show an increase in frequency when increasing compressive strain by reducing film thickness; this is due to the shrinking of the unit cell volume. Such behavior is in qualitative agreement with recent ab initio calculations, although the measured values are significantly smaller than predictions. In contrast, the measured Poisson ratio is found to be in good agreement with expectations based on general arguments of atomic packing density. Possible guidelines for searching auxetic response in materials with spinel structure are discussed.