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Title: Thermal effect on magnetic parameters of high-coercivity cobalt ferrite

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 (H{sub C}) 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 H{sub C}. Furthermore, this thermal treatment increases the size of the nanoparticles and, as a consequence, there is a substantial increase in the saturation magnetization (M{sub S}). The H{sub C} of the samples treated at 600 °C for 30 and 180 min were 2.24 and 1.93 kOe, respectively, and the M{sub S} of these same samples increased from 57 emu/g to 66 and 70 emu/g, respectively. The H{sub C} and the M{submore » S} are less affected by the thermal treatment at 300 and 400 °C.« less
Authors:
; ; ;  [1] ;  [2] ;  [3]
  1. Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá-MT (Brazil)
  2. Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970 Campinas (Brazil)
  3. Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150 Urca. Rio de Janeiro (Brazil)
Publication Date:
OSTI Identifier:
22308915
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 77 NANOSCIENCE AND NANOTECHNOLOGY; COBALT COMPOUNDS; COERCIVE FORCE; COMBUSTION; CRYSTAL DEFECTS; DENSITY; FERRITES; HEAT TREATMENTS; HYSTERESIS; MAGNETIZATION; MICROSTRUCTURE; NANOPARTICLES; SATURATION; STRAINS; TEMPERATURE RANGE 0400-1000 K; TRANSMISSION ELECTRON MICROSCOPY