Electromagnetic properties of nanocrystalline Al3+ substituted MgCuMn ferrites synthesized by microwave hydrothermal method

The effect of Al3+ substitution on electromagnetic properties has been studied for nanocrystalline Mg0.8Cu0.2Mn0.05Al x Fe1.95−x O4 ferrites, wherein x varies from 0 to 0.4 in steps of 0.1. These ferrites were synthesized by using microwave hydrothermal method and then characterized using X-ray diffractometer (XRD), Fourier transform infrared and transmission electron microscopy. The synthesized powders were densified using microwave sintering method at 950∘C/50 min. Structural and surface morphology of sintered samples were characterized using XRD and atomic force microscopy, respectively. The complex permittivity and permeability properties were measured over a frequency range 100 Hz–1.8 GHz. The temperature variation of magnetic properties were measured in the temperature range of 300–650 K. The electrical and magnetization studies inferred that the values of d.c. resistivity increases by 27%, whereas saturation magnetization decreases linearly from 38.6 to 23.0 emu g−1 and Curie temperature was found to be decreased from 628 to 513 K with an increase of Al3+ ions. The low dielectric, magnetic losses, moderate saturation magnetization and high-temperature stability properties exhibited by Al3+ substituted MgCuMn ferrites make them find applications in microwave devices, such as circulators and isolators etc. The applicability of present samples for microwave devices has been tested by the measurement of ferromagnetic resonance linewidth at Ka band.