Magnetic and magnetostrictive properties of RE-doped Cu-Co ferrite fabricated from spent lithium-ion batteries

Magnetostrictive Cu0.1Co0.9RExFe2-xO4 (RE=Ho, Gd or Sm) was fabricated by a sol-gel auto-combustion technique using spent lithium-ion batteries as raw materials. X-ray diffraction analysis confirmed the spinel structure of the RE-incorporated samples with limited RE solubility. Field-emission scanning electron microscopy and Fourier transform infrared spectroscopy revealed a layered structure composed of particles and the cation distribution. Magnetic hysteresis loops and magnetostriction strain curves showed that the saturation magnetization, magnetostriction coefficient and strain derivative were significantly modified due to the substitution of larger ionic radius RE3+ ions for Fe3+ ions, influencing the interaction between the tetrahedral and octahedral sites.