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<p>Nanocrystalline Ni<sub>0.9−<i>x</i></sub>Zn<sub>0.1</sub>Co<sub><i>x</i></sub>Fe<sub>2</sub>O<sub>4</sub> (<i>x</i> = 0.2, 0.4, 0.6, 0.8) ferrites were synthesized via the sol–gel method, yielding a cubic single-phase spinel structure (Fd−3m), as confirmed through Rietveld refinement. The crystallite size was observed to increase from 7 to 10&#xa0;nm with higher Co substitution. Magnetic characterization revealed a pronounced dependence on Co concentration, with zero-field-cooled and field-cooled magnetization curves exhibiting bifurcation indicative of magnetic relaxation phenomena. The Ni<sub>0.5</sub>Zn<sub>0.1</sub>Co<sub>0.4</sub>Fe<sub>2</sub>O<sub>4</sub> composition exhibited a blocking temperature of 191&#xa0;K, a Curie temperature of 207&#xa0;K, and a transition from ferromagnetic ordering at 5&#xa0;K to superparamagnetic behavior at 300&#xa0;K. Similarly, Ni<sub>0.3</sub>Zn<sub>0.1</sub>Co<sub>0.6</sub>Fe<sub>2</sub>O<sub>4</sub> demonstrated a transition at 251&#xa0;K with retained ferromagnetic ordering at 5&#xa0;K. In contrast, Ni<sub>0.1</sub>Zn<sub>0.1</sub>Co<sub>0.8</sub>Fe<sub>2</sub>O<sub>4</sub> displayed magnetic irreversibility and a paramagnetic state at 300&#xa0;K. Raman spectroscopy further corroborated the inverse spinel structure, revealing characteristic vibrational modes at ~ 460&#xa0;cm⁻<sup>1</sup> and 680&#xa0;cm⁻<sup>1</sup>. These findings underscore the pivotal role of Co substitution in modulating the structural and magnetic properties of Ni<sub>0.9−<i>x</i></sub>Zn<sub>0.1</sub>Co<sub><i>x</i></sub>Fe<sub>2</sub>O<sub>4</sub> nanocrystals, particularly their temperature-dependent magnetic phase transitions. Collectively, the results highlight the influence of Co concentration on the structural and magnetic properties of Ni<sub>0.9−<i>x</i></sub>Zn<sub>0.1</sub>Co<sub><i>x</i></sub>Fe<sub>2</sub>O<sub>4</sub> nanocrystals, particularly their temperature-dependent magnetic transitions.</p>

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Cobalt Concentration-Dependent Structural and Magnetic Transitions in Nanocrystalline Ni0.9−xZn0.1CoxFe2O4 Ferrites

  • 期刊论文

  • 发表日期：

    2025年6月1日

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  • K. K. Palsaniya,
  • Anchal,
  • Sarita,
  • M. S. Rulaniya,
  • Pooja Yadav,
  • R. K. Beniwal,
  • Namita Kumari,
  • P. A. Alvi,
  • B. L. Choudhary

摘要

Nanocrystalline Ni0.9−xZn0.1CoxFe2O4 (x = 0.2, 0.4, 0.6, 0.8) ferrites were synthesized via the sol–gel method, yielding a cubic single-phase spinel structure (Fd−3m), as confirmed through Rietveld refinement. The crystallite size was observed to increase from 7 to 10 nm with higher Co substitution. Magnetic characterization revealed a pronounced dependence on Co concentration, with zero-field-cooled and field-cooled magnetization curves exhibiting bifurcation indicative of magnetic relaxation phenomena. The Ni0.5Zn0.1Co0.4Fe2O4 composition exhibited a blocking temperature of 191 K, a Curie temperature of 207 K, and a transition from ferromagnetic ordering at 5 K to superparamagnetic behavior at 300 K. Similarly, Ni0.3Zn0.1Co0.6Fe2O4 demonstrated a transition at 251 K with retained ferromagnetic ordering at 5 K. In contrast, Ni0.1Zn0.1Co0.8Fe2O4 displayed magnetic irreversibility and a paramagnetic state at 300 K. Raman spectroscopy further corroborated the inverse spinel structure, revealing characteristic vibrational modes at ~ 460 cm⁻1 and 680 cm⁻1. These findings underscore the pivotal role of Co substitution in modulating the structural and magnetic properties of Ni0.9−xZn0.1CoxFe2O4 nanocrystals, particularly their temperature-dependent magnetic phase transitions. Collectively, the results highlight the influence of Co concentration on the structural and magnetic properties of Ni0.9−xZn0.1CoxFe2O4 nanocrystals, particularly their temperature-dependent magnetic transitions.