Highly sensitive magnetostrictive NiZnCo ferrites for low magnetic field sensor applications

Ferrites with enhanced magnetostrictive strain and sensitivity possess significant potential for various multifunctional devices. Herein, the magnetostrictive ferrites (Ni_0.8Zn_0.2)_1-<i>x</i>Co_<i>x</i>Fe₂O₄ (0 ≤ <i>x</i> ≤ 1) are prepared by a facile sintering method. The X-ray diffraction and scanning electron microscope results demonstrate that the lattice constant and mean grain size increase with <i>x</i> while the porosity decreases. Through magnetic measurements, it is found that the saturation magnetization, coercivity and magnetocrystalline anisotropy constant, all increase with <i>x</i>. However, the permeability decreases due to the inherent hard magnetic nature of cobalt ferrite. Magnetostrictive strain measurements reveal that with the increasing <i>x</i>, the saturation magnetostrictive strain is elevated, owing to the strong magnetocrystalline anisotropy of the octahedrally coordinated Co²⁺. The strain sensitivity variation of the samples with 0.2 ≤ <i>x</i> ≤ 0.8 is consistent with the theoretical parameter. The maximum strain sensitivity is achieved in the sample with <i>x</i> = 0.4 (0.229 ppm Oe^-1), and the magnitude of the external magnetic field is also the smallest at this time, which indicates that this material may be applied in the field of low magnetic field magnetoelectric sensors and devices. Finally, in order to further optimise the properties of magnetostrictive materials, an innovative approach is introduced.