Spherical (ZnδNi1-δFe2O4)γ nanoparticles in an amorphous (SiO2)1-γ matrix, prepared with the sol–gel method
✍ Scribed by C. Caizer; M. Popovici; C. Savii
- Book ID
- 104403072
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 217 KB
- Volume
- 51
- Category
- Article
- ISSN
- 1359-6454
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✦ Synopsis
By using the sol-gel method we have obtained spherical nanoparticles (NPs) of stoichiometric (Zn d Ni 1-d Fe 2 O 4 ) γ mixed ferrite (d = 0.15; 0.35; 0.65 and g = 0.15), dispersed in an amorphous (SiO 2 ) 1-g matrix (nanocomposites). The nanocomposites were investigated at room temperature by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), Mo ¨ssbauer spectroscopy and quasi-static magnetic measurements. We have studied in detail the magnetic behavior of ferrite NPs in a silica matrix, both under quasi-static (50 Hz) and dynamic (20 MHz) conditions. The results show a pure superparamagnetic (SPM) behavior of the sample that has a concentration of the Zn ions of d = 0.15. At higher concentrations, there is a significant deviation from this behavior and this deviation increases with the increase of d. We attribute the observed behavior to the Ne ´el-type magnetic relaxation processes. After processing the TEM image and performing magneto-granulometric measurements, it has resulted that on the surface of NPs embedded in the silica matrix a layer is formed; this layer has a thickness in the size range of nanometers and it has no magnetic ordering.