Structural, Optical, and Magnetic Properties of Mn x Fe 3‐x O 4 Ferrofluids Derived From Iron Sand for Energy Harvesting Application

In this research, we report the synthesis of iron sand‐based Mn x Fe 3‐x O 4 ferrofluids along with the characterization of their structural, optical, and magnetic properties, as well as their energy harvesting performance. The Mn x Fe 3‐x O 4 nanoparticles in the ferrofluids constructed an inverse spinel structure, with their diffraction peaks shifting to lower angles as the Mn 2+ content increased. FTIR spectra showed the Fe‐O and Mn‐O stretching detected at wavenumbers of 430–521 cm −1 and 411 cm −1 , respectively. The magnetic nanoparticles tended to agglomerate with particle sizes ranging from 24.0 nm to 39.6 nm. The bandgap energy increased as the Mn 2+ content increased. Furthermore, the energy harvesting performance was represented by voltage values in the range of 16.17–96.20 µV as a function of Mn 2+ content. Although the voltage was relatively low, the obtained results indicate promising potential for future energy harvesting applications.