Journal
JOURNAL OF ELECTRICAL ENGINEERING-ELEKTROTECHNICKY CASOPIS
Volume 70, Issue 7, Pages 71-76Publisher
SLOVAK UNIV TECHNOLOGY
DOI: 10.2478/jee-2019-0044
Keywords
iron oxide; hematite (alpha - Fe2O3); sol-gel synthesis; superparamagnetism (SPION); Morin transition; particle size effects
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Funding
- Ministry of Education, Science and Technology of the Republic of Serbia [III 45015, III 044006]
- Ministry of Higher Education, Science and Technology of the Republic of Slovenia within the National Research Program
- Serbian-Slovenian bilateral project [BI-RS/16-17-030]
- Serbian-Austrian bilateral project [451-03-02141/2017-09/10]
- Serbia-Slovakia bilateral project [SK-SRB-2016-0055]
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Using the sol-gel method we synthesized hematite (alpha - Fe2O3) nanoparticles in a silica matrix with 60 wt % of hematite. X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the sample demonstrate the formation of the alpha - Fe2O3 phase and amorphous silica. A transmission electron microscopy (TEM) measurements show that the sample consists of two particle size distributions of the hematite nanoparticles with average sizes around 10 nm and 20 nm, respectively. Magnetic properties of hematite nanoparticles were measured using a superconducting quantum interference device (SQUID). Investigation of the magnetic properties of hematite nanoparticles showed a divergence between field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves and two maxima. The ZFC magnetization curves displayed a maximum at around T-B = 50 K (blocking temperature) and at T-M = 83 K (the Morin transition). The hysteresis loop measured at 5 K was symmetric around the origin, with the values of coercivity, remanent and mass saturation magnetization H-C10K approximate to 646 A/cm, (810 Oe), M-r10K = 1.34 emu/g and M-S10K = 6.1 emu/g respectively. The absence of both coercivity (H-C300K = 0) and remanent magnetization (M-r300K = 0) in M(H) curve at 300 K reveals super-paramagnetic behavior, which is desirable for application in biomedicine. The bimodal particle size distributions were used to describe observed magnetic properties of hematite nanoparticles. The size distribution directly influences the magnetic properties of the sample.
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