Chemically enabling CoFe2O4 for magnetostrictive strain sensing applications at lower magnetic fields: Effect of Zn substitution

Abstract Phase pure cobalt-ferrite (CoFe2O4) and Zn-substituted CoFe2O4 (Co0.8Zn0.2Fe2O4 and CoFe1.8Zn0.2O4) nanopowders were synthesized by a glycine-nitrate auto-combustion route without any post-calcination process. The as-synthesized nano-ferrite powders were first pelletized, sintered and studied. Our results show that the crystallographic site preference of Zn, cation distribution, change in the oxidation state of Co-cation (+2 to + 3), and reduction in magnetic A-O-B superexchange interactions of the AB2O4 type spinel structure have a direct consequence on the excellent magnetostriction behavior of the samples. Our results demonstrate that although the observed λmax values of the Zn-substituted samples are lower than the unsubstituted sample, importantly, the magnitude of the maximum strain sensitivity ([dλ/dH]max) of the Zn-substituted samples (~3.6 × 10-9 m/A) is nearly 300% higher than the parent compound (~1.18 × 10-9 m/A), even at remarkably low magnetic fields. This facilitates the direct use of our samples for highly sensitive strain sensor applications.