Preparation and structural, optical, magnetic, and electrical characterization of Mn2+/Co2+/Cu2+ doped hematite nanocrystals

• Pure and Mn/Co/Cu-doped hematite nanocrystals have been prepared.
• The method adopted for the preparation is simple, economical and scalable.
• Prepared nanocrystals are spherical in shape with good crystallinity and phase purity.
• Mn/Co/Cu-doping enhances the optical transmittance and ferromagnetic order.
• Optical, magnetic and electrical properties tuned by Mn/Co/Cu-doping are explained.

Pure and Mn2+ / Co2+ / Cu2+ doped (1 and 2 at.%) spherical hematite (α-Fe2O3)nanocrystals have been synthesized by a simple solvothermal method using a domestic microwave oven. XRD measurements confirm that all the seven nanocrystals prepared consist of nanocrystalline hematite phase without any other phases. The energy dispersive X-ray and Fourier transform infrared spectral analyses confirm the phase purity of the nanocrystals prepared. TEM analysis shows the average particle sizes within the range 33–51 nm. Optical absorption measurements indicate that all the three dopants enhance the optical transmittance and reflectance. A red shift is observed in the bandgap energy values estimated from optical absorption and reflectance spectra. Results of magnetic measurements made at room temperature using a vibrating sample magnetometer indicate significant changes in the magnetic properties (coercivity, retentivity and saturationmagnetization) due to doping. Results of magnetic measurements indicate significant changes in the magnetic properties. Results of AC electrical measurements made at various temperatures in the range 40–130 °C and frequencies in the range 100 Hz –1 MHz indicate low dielectric constants and AC electrical conductivities and consequently show the occurrence of nanoconfined states.

The indexed X-ray diffraction (XRD) patterns of all the seven nanocrystals indicate the rhombohedral structure of hematite (JCPDS card No.13-0534). No impurity phase like oxides of Mn or Co or Cu was detected above equipment limit. The average crystallite (grain) sizes estimated using the Scherrer's formula.Figure optionsDownload as PowerPoint slide