High room temperature coercivity from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si56.svg" display="inline" id="d1e603"><mml:mi>α</mml:mi></mml:math>-Fe2O3 nanoparticles embedded in silica

Abstract

Hematite ( α -Fe 2 O 3 ) nanoparticles embedded in SiO 2 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 ( α -Fe 2 O 3 / SiO 2 ). 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 ( H ) 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 C ∼ 8.5 kOe for the α -Fe 2 O 3 / SiO 2 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. • The article explores the magnetic properties of hematite nanoparticles with sub-particle structure. • The article is one of the latest reports reporting on a novel large coercivity in hematite ∼ 8.5 kOe. • The article combines XRD, TEM, Mössbauer spectroscopy, and vibrating sample magnetometer (VSM).