Verwey transition temperature distribution in magnetic nanocomposites containing polydisperse magnetite nanoparticles
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Polymeric nanocomposites containing Fe3O4 nanoparticles were prepared through a chemical route under different precursor-to-solvent ratios and were submitted to structural and morphologic characterization. The embedded nanoparticles, containing pure magnetite and characterized by considerable polydispersity, are rather homogeneously dispersed in the matrix. The magnetic properties of two representative samples were analyzed in detail between T = 5 K and room temperature. Magnetic effects clearly associated with the Verwey monoclinic to cubic transition with transition temperatures distributed in the interval 95–120 K were put in evidence. On heating through this region, the coercive field and the maximum susceptibility of hysteresis loops display marked downward/upward steps, respectively, while the high-field magnetization is not affected at all; a comparable upward step is measured in the FC/ZFC curves. Reporting the maximum susceptibility as a function of the reciprocal of the coercive field in the interval from T = 95 to T = 120 K, and using the predictions for single-domain nanoparticles with randomly distributed axes of uniaxial and cubic anisotropy (the former/latter case being applicable below/above the Verwey transition, respectively), the evolution of the transformed cubic-anisotropy fraction upon heating has been studied, and the distribution of Verwey transition temperatures related to the sample polydispersity has been accurately determined. The low-temperature value of the uniaxial anisotropy constant is obtained from coercive field measurements and found to be comparable to, albeit slightly higher than the corresponding quantity measured in bulk crystalline magnetite.
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- 18.Sciancalepore C, Gualtieri AF, Scardi P et al (2018) Structural characterization and functional correlation of Fe3O4 nanocrystals obtained using 2-ethyl-1,3-hexanediol as innovative reactive solvent in non-hydrolytic sol-gel synthesis. Mater Chem Phys 207:337–349. https://doi.org/10.1016/j.matchemphys.2017.12.089 CrossRefGoogle Scholar
- 20.Sciancalepore C, Bondioli F, Messori M et al (2015) Epoxy nanocomposites functionalized with in situ generated magnetite nanocrystals: microstructure, magnetic properties, interaction among magnetic particles. Polymer (UK) 59:278–289. https://doi.org/10.1016/j.polymer.2014.12.047 CrossRefGoogle Scholar
- 34.Sciancalepore C, Bondioli F, Manfredini T, Gualtieri A (2015) Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis. Mater Charact 100:88–97. https://doi.org/10.1016/j.matchar.2014.12.013 CrossRefGoogle Scholar
- 38.Chikazumi S (1997) Physics of ferromagnetism. Oxford University Press, OxfordGoogle Scholar