| 1. |
|
|
| 2. |
- Ozkaya, T., et al.
(författare)
-
A novel synthetic route to Mn3O4 nanoparticles and their magnetic evaluation
- 2008
-
Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 403:19-20, s. 3760-3764
-
Tidskriftsartikel (refereegranskat)abstract
- Manganese oxide (Mn3O4) nanoparticles were successfully prepared by a novel oxidation-precipitation method based on oxidation of manganese sulfate to manganese salts and hydrolyzing with NaOH and concentrated NH3. X-ray diffraction (XRD) analysis confirmed the tetragonal haussmanite structure with average crystallite size of similar to 14 and similar to 11 nm: transmission electron microscopy (TEM) analysis showed crystallite size of 14 5 and 12 3 nm for NaOH- and NH3-hydrolyzed samples, respectively. The ferromagnetic transition temperatures are 38 and 40 K for NaOH- and NH3-hydrolyzed samples, respectively. These values are lower than that of bulk Mn3O4. Both samples show superparamagnetic behavior at room temperature, with no apparent saturation magnetization and hysteresis in the region of measured field strength, and they also exhibit relatively large coercivity below the ferromagnetic transition temperature. Below the transition, marked differences are observed in temperature dependence of magnetization, hysteresis loop shape, and type of the samples from the bulk values. The particles are considered as single magnetic domains with random orientations of magnetic moments and thermal fluctuations of anisotropic axes. These results are attributed to the smaller size (increase in surface to volume ratio) of the samples, which cause an increase of effective magnetic surface anisotropy.
|
|
| 3. |
- Ozkaya, T., et al.
(författare)
-
Reflux synthesis of Co3O4 nanoparticles and its magnetic characterization
- 2009
-
Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 321:14, s. 2145-2149
-
Tidskriftsartikel (refereegranskat)abstract
- Co3O4 nanoparticles have been prepared for the first time via reflux method, as an alternative low-temperature high-yield process, starting from one single precursor. A plausible mechanism is suggested for the synthetic process. XRD, TEM, FTIR and VSM were used for the structural, morphological, spectroscopic, and magnetic characterization of the product respectively. X-ray diffraction line profile fitting showed that average particle size of the sample is 28 nm. Morphology of the synthesized powder was observed to be thin nanosheets with a thickness of 2-3 nm based on SEM and TEM analyses. Magnetic measurements showed a deviation of the Neel temperature from the bulk value which is attributed to the finite size effects. A loop shift with an enhanced coercivity is observed in the field-cooled hysteresis loops. The opening of the hysteresis loop reveals the existence of the spin-glass like surface spins of the Co3O4 nanoparticles.
|
|
