Spin dynamics investigations of multifunctional ambient scalable Fe₃O₄ surface decorated ZnO magnetic nanocomposite using FMR

Microwave spin resonance behavior of the Fe₃O₄ surface decorated ZnO nanocomposites (FZNC) has been investigated by ferromagnetic resonance (FMR). Modified hydrothermal method has been adopted to fabricate FZNC samples with Fe₃O₄ nanoparticles chains were used as seeds in the uniform magnetic field to decorate them on the surface of the ZnO nanoparticles in a unique configuration. Spin dynamics investigation confirms the transition of ZnO from diamagnetic to ferromagnetic as the sharp FMR spectra converts to the broad spectra with Fe₃O₄ nanoparticles incorporation. A single broad FMR spectra confirms that no isolated Fe³⁺ or Zn²⁺ ions exist which is also in agreement with XRD confirming suitable composite formation. Further, the increase in Fe₃O₄ concentration leads to decrease in g-value which is resulting from the internal field enhancement due to magnetic ordering. Also, various spin resonance parameters were calculated for the FZNC which provides a detail information about the magnetic ordering, exchange coupling and anisotropy. Elemental analysis confirms the presence of Fe and Zn simultaneously and transmission electron microscopy (TEM) image show the presence of Fe₃O₄ on the grain boundaries of ZnO which has been confirmed by taking high-resolution TEM and electron diffraction patterns on both sides of the interface. These unique structural configuration of the FZNC has tremendous potential in various magneto-optoelectronic, spintronics and electro-chemical applications.