High room temperature coercivity from α-Fe2O3 nanoparticles embedded in silica

Abstract

Hematite ($\alpha$-Fe₂O₃) nanoparticles embedded in SiO₂ matrix have been synthesized using Sol–gel method at 1100 °C to investigate the correlation between structural and magnetic properties. X-ray diffraction analysis revealed the formation of a single phase hematite in silica matrix ($\alpha$-Fe₂O₃/ SiO₂). Transmission electron Microscopy has confirmed homogeneous spherical morphology of dimensions (118 +/- 28) nm. The room temperature Mössbauer spectroscopy revealed the weakly ferromagnetic state in the sample. The spectra was fitted with a model consisting of a single Lorentzian-shaped sextet with the Mössbauer parameters; the isomer shift of 0.37 mm/s, quadrupole shift of -0.10 mm/s, and the magnetic hyperfine field of 51.5 T. $M\left(H\right)$ magnetization curves (hysteresis loops) were recorded at 10, 100, 200 and 300 K for the sample. Room temperature magnetization measurements revealed a surprisingly high coercivity field of $H_{\text{C}}$ $\sim$ 8.5 kOe for the $\alpha$-Fe₂O₃/ SiO₂ nanoparticles, and this was explained using the sub-particle structure model. A room temperature remanent magnetization of M${}_r$ = 0.27 emu/g and saturation magnetization M${}_s$ = 1.90 emu/g were recorded for this sample.