Magnetic and magnetoelastic properties of Zn-dopedcobalt-ferrites â•flCoFe2â‹TMxZnxO4 (x = 0, 0.1, 0.2, and 0.3)

Cobalt-ferrite (CoFe2O4) based materials are suitable candidates for magnetomechanical sensor applications owing to a strong sensitivity of their magnetostriction to an applied magnetic field. Zn-doped cobalt-ferrites, with nominal compositions CoFe2−xZnxO4 (x = 0–0.3), were synthesized by auto-combustion technique using Co, Fe, and Znnitrate as precursors. X-ray spectra analysis and Transmission electron microscopy studies revealed that the as-prepared powders were comprised of nano-crystalline (~25–30 nm) cubic-spinel phase with irregularly-shaped grains morphology along with minor impurity phases. Calcination (800 °C for 3 h) of the precursor followed by sintering (1300 °C for 12 h) resulted in a single phase cubic-spinel structure with average grain size ~2–4 μm, as revealed from scanning electron micrographs. The magnitude of coercive field decreases from ~540 Oe for x = 0 to 105 Oe for x = 0.30. Saturation magnetization initially increases and peaks to ~87 emu/g for x = 0.2 and then decreases. The peak value of magnetostriction monotonically decreases with increasing Zn content in the range 0.0–0.3; however the piezomagnetic coefficient (dλ/dH) reaches a maximum value of 105×10−9 Oe−1 for x = 0.1. The observed variation in piezomagnetic coefficient in the Zn substituted cobalt ferrite is related to the reduced anisotropy of the system. The Zndoped cobalt-ferrite (x = 0.1) having high strain derivative could be a potential material for stress sensor application.