Observation on magnetic variation for low concentration of bismuth and samarium doped Ni-Co ferrites

Samarium and bismuth are doped in lower concentration in Ni0.7Co0.3Fe2−xRxO4 (x = 0, 0.02, 0.04, 0.06) (R = Sm or Bi) and are prepared using ceramic route and sintered at 1150 °C for 4 h. X-ray diffraction confirms the cubic structure without any distortion for higher ionic radii ions in the spinel structure. High strain is observed for Ni0.7Co0.3Fe1.98Bi0.02O4 among investigated samples. Field-emission scanning electron microscope (FE-SEM) confirms the doping of bismuth and samarium in expected ratio for Rx-Ni-Co ferrites. Low concentration doping effects were characterized using spectroscopic techniques, by which four primary bands were noted from Fourier transform infrared (FTIR) and Raman spectroscopy. Saturation magnetization decreases for lower concentrated ions, substituted in Ni-Co ferrites, saturation magnetization shows increase in higher concentration, attributing to changes that occur due to exchange interactions. Coercivity increases with the increase in samarium but decreases with bismuth substitution.