Strain and Exchange‐Spring Mechanism of (1‐x) Ni_0.5Cu_0.25Zn_0.25Fe₂O₄ + (x) SrFe₁₁Y₁O₁₉ Magnetically Soft–Hard Ferrite Composed Nanoparticles

Abstract A mixture of soft–hard (S–H) ferrites with the general chemical formula (1‐x) Ni_0.5Cu_0.25Zn_0.25Fe₂O₄ (NCZFO) + (x) SrFe₁₁Y₁O₁₉ (SFYO) is developed via sol‐gel auto‐combustion and their physical mixing. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, field emission scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy, high‐resolution transmission electron microscopy (HRTEM), vibrating sample magnetometry (VSM) and two‐probe technique are used to examine the resultant materials. Rietveld refinement of XRD data confirms the co‐existence of both soft and hard phases in the composites. The HRTEM and FESEM results confirm the nanocrystalline nature of the synthesized particles. Williamson‐Hall method is employed to reveal the strain nature in soft and hard phases. VSM analysis shows considerable changes in the magnetic characteristics for the different composition of NCZFO and SFYO. The exchange‐spring mechanism is discussed in the manuscript.