Tuning the magnetocrystalline anisotropy and spin dynamics in CoxZn1-xFe2O4 (0 ≤ x ≤ 1) nanoferrites

The present work investigates the static and dynamic magnetization behaviour of Co-Zn nanoferrites and optimizes the magnetocrystalline anisotropy and spin relaxation time. The CoxZn1-xFe2O4 (0 ≤ x ≤ 1) magnetic nanoparticles are synthesized by pH-controlled co-precipitation method. The Le Bail structural refinement of X-ray diffraction patterns confirms the single phase formation with negligible synthesis dependent site inversion. The room temperature static dc magnetization study shows a continuous transition from hard ferrimagnetic CoFe2O4 to soft and weakly magnetic ZnFe2O4, which has been successfully explained with Yafet-Kittel model. Furthermore, approach-to-saturation analysis gives effective magnetocrystalline anisotropy of 1.45 × 104 J/m3 and lowest anisotropy field of 1.3 kOe for x = 0.4. Next, the dynamic magnetization is studied with Electron Spin Resonance spectroscopy. The lineshape analysis gives highest g-value of 3.88 and lowest spin-relaxation time (T2) of 4.86 × 10−12 s for x = 0.4, which is in agreement with static magnetization study. The optimized magnetocrystalline anisotropy and lowest spin-relaxation time for Zn0.4Co0.6Fe2O4 make it a good candidate for use in different biomedical applications.