Tailoring magnetic properties of α-MnO₂@NiCo₂O₄ core/shell nanostructure

Herein, we present a bi-magnetic hierarchical α-MnO₂@NiCo₂O₄ core–shell nanostructure synthesized through a simple two-step hydrothermal process. The structural and morphological properties of these core–shell nanostructures were studied systematically using X-ray diffraction and Field emission scanning electron microscope. The XRD patterns are concomitant with the presence of the two phases, and the formation of nanowire@nanosheet is confirmed by the SEM/EDX study. FTIR measurement results give an idea about the vibration and bond formation of the samples, while the optical properties of the samples examined through UV–visible spectroscopy suggest the presence of a spinel group along with the MnO₂ phase in the absorption spectra. The results of magnetic measurements reveal the spin-glass type behavior at very low temperature i.e., 8 K, and the saturation magnetization for the core–shell system was found to be 50 emu/g. Experimental evidence for this spin glass behavior was confirmed by the studies of memory cycles and the relaxation dynamics in thermal variation of the magnetization process.