Thermal effect on magnetic parameters of high-coercivity cobalt ferrite
| Autor: | R. J. Prado, A. S. Ponce, E. F. Chagas, G. M. Silva, E. Baggio-Saitovitch, Jefferson Bettini |
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| Jazyk: | angličtina |
| Rok vydání: | 2014 |
| Předmět: |
Condensed Matter - Materials Science
Materials science Condensed Matter - Mesoscale and Nanoscale Physics Annealing (metallurgy) Analytical chemistry General Physics and Astronomy Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences Thermal treatment Coercivity Magnetic hysteresis Microstructure Magnetization Mesoscale and Nanoscale Physics (cond-mat.mes-hall) Magnetic nanoparticles Saturation (magnetic) |
| Popis: | We prepared very high-coercivity cobalt ferrite nanoparticles synthesized by a combustion method and using short-time high-energy mechanical milling to increase strain and the structural defects density. The coercivity (HC) of the milled sample reached 3.75 kOe—a value almost five times higher than that obtained for the non-milled material (0.76 kOe). To investigate the effect of the temperature on the magnetic behavior of the milled sample, we performed a thermal treatment on the milled sample at 300, 400, and 600 °C for 30 and 180 min. We analyzed the changes in the magnetic behavior of the nanoparticles due to the thermal treatment using the hysteresis curves, Williamson-Hall analysis, and transmission electron microscopy. The thermal treatment at 600 °C causes decreases in the microstructural strain and density of structural defects resulting in a significant decrease in HC. Furthermore, this thermal treatment increases the size of the nanoparticles and, as a consequence, there is a substantial increase in the saturation magnetization (MS). The HC of the samples treated at 600 °C for 30 and 180 min were 2.24 and 1.93 kOe, respectively, and the MS of these same samples increased from 57 emu/g to 66 and 70 emu/g, respectively. The HC and the MS are less affected by the thermal treatment at 300 and 400 °C. |
| Databáze: | OpenAIRE |
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