Impact of Dy on the microstructural, electrical, and magnetic properties of topological Fe_1.4Bi_0.6Y_0.5Se_{2.5−<i>x</i>} nanocrystals

Nanoparticles of Dy-doped Fe_1.4Bi_0.6Y_0.5Se_2.5-<i>x</i> (<i>x</i> = 0, 0.1, 0.2, 0.3) were synthesized using the sol-gel method. The effects of Dy doping on the microstructural, thermal, magnetic, and electrical properties of Fe_1.4Bi_0.6Y_0.5Se_2.5-<i>x</i> nano-crystallites were investigated. X-ray diffraction (XRD) analysis confirmed higher crystallinity in undoped Fe_1.4Bi_0.6Y_0.5Se_2.5. At higher Dy concentrations (<i>x</i>: 0.1, 0.2, 0.3), a few peaks corresponding to the DyFeO₃ phase appeared. Morphological analyses (SEM/TEM) and FTIR spectra revealed Dy-induced microstructural modifications, including an increase in particle size to 25-27 nm and alterations in Bi-O-Dy vibrations. Thermal analysis demonstrated dehydration-induced weight loss and excellent thermal stability up to 600 °C. Magnetic measurements indicated a transition from ferromagnetic to superparamagnetic with Dy doping, alongside superparamagnetic tendencies at higher Dy concentrations. Electrical measurements showed a transition from semiconducting to metallic behavior, with conductivity increasing at higher frequencies and temperatures, suggesting thermally activated conduction mechanisms. These findings confirm that Dy³⁺ incorporation significantly influences the internal structure of Bi_0.6Fe_1.4Se_2.5Y_0.5 nanoceramics, enhancing their magnetoelectric properties. The improved structural, thermal, magnetic, and electrical characteristics make Dy-doped Bi_0.6Fe_1.4Se_2.5Y_0.5 nanoceramics promising candidates for applications in microelectronics, topological quantum devices, and spintronics.