Improved magnetostrictive properties of cobalt ferrite (CoFe2O4) by Mn and Dy co-substitution for magneto-mechanical sensors

The present study explores the effect of Dy3+ rare-earth ion substitution on the crystal structure, morphology, and magnetic properties of magnetostrictive Co0.7Mn0.3Fe2O4 spinel ferrite and demonstrates their potential applications in magnetomechanical sensors. The intrinsic CoFe2O4 and Dy-substituted Co0.7Mn0.3Fe2-xDyxO4 (x = 0.0-0.1) were prepared by the standard solid-state chemical reaction method. Xray diffraction studies along with the Rietveld refinement confirm that all the samples exhibit single-phase cubic spinel structure with space group Fd (3) over barm. Raman and Mossbauer data analyses reveal that the cation redistribution with Mn and Dy cosubstitution in CoFe2O4 and confirm the presence of a mixed spinel structure. Electron microscopy analysis indicates the significant effect of Mn, Dy cosubstitution on the microstructure of CoFe2O4. All the samples exhibit the magnetic hysteresis (M-H) loops at 5 K and 300 K. Saturation magnetization (M-s) and the cubic anisotropy constant (K-1) values increase with Mn substitution, while with Dy substitution, Ms reduces due to the decrease of magnetic interactions with Dy substitution. However, the coercive field decreases with Mn and increases with Dy substitution. Higher values of magnetostriction coefficients (lambda(11) = -95 ppm and lambda(12) = 52 ppm) and the strain derivative (d lambda/dH = 0:075 ppm=Oe at 600 Oe) observed make Co0.7Mn0.3Fe1.95Dy0.05O4 a suitable candidate for designing torque/stress sensors and a magnetostrictive phase for making magnetoelectric composite. Chemical composition optimization yields higher values Ms (89 emu/g, i.e., 3.73 mu B) at lower coercivity (Hc = 241 Oe) for Co0.7Mn0.3Fe2O4 and higher values of lambda(11), lambda(12), and d lambda/dH at a lower magnetic field (below 800 Oe) for Co0.7Mn0.3Fe1.95Dy0.05O4. The results suggest and demonstrate that Co0.7Mn0.3Fe2O4 and Co0.7Mn0.3Fe1.95Dy0.05O4 are the potential candidates for designing magnetomechanical sensor applications. Published under license by AIP Publishing.