Magnetic investigation of iron-nitride-based magnetic fluid
Transmission electron microscopy (TEM), Mössbauer spectroscopy and magnetization measurements were used in the present study to investigate a non-aqueous iron-nitride-based magnetic fluid (MF) sample containing about 2 × 1016 particle/cm3. The TEM micrographs indicated spherical-shaped iron nitride nanoparticles with an average diameter of 12.3 nm and diameter dispersity of 0.14. The 77 K Mössbauer spectrum of the frozen MF sample indicated the presence of about 95% of the γ′-Fe4N phase, with a residual 5% of the ɛ-Fe4N phase. The temperature dependence of the magnetization was investigated under zero-field-cooled (ZFC) condition, in the temperature range of 4 to 165 K. The ZFC-data were curve-fitted using a new approach that takes into account the particle size distribution and the temperature dependence of the magnetocrystalline anisotropy, making the description of the experimental situation more realistic.
KeywordsTransmission electron microscopy Mössbauer spectroscopy Zero-field-cooled magnetization Magnetic fluids
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