Structural and magnetic properties of cobalt ferrite nanoparticles synthesized by co-precipitation at increasing temperatures

Author(s)

Stein, C. R. ^{[1, 2]} ; Bezerra, M. T. S. ^[2] ; Holanda, G. H. A. ^[2] ; Andre-Filho, J. ^[1] ; Morais, P. C. ^{[1, 3]}

Affiliation

^[1] Univ Brasilia, Inst Phys, BR-70910900 Brasilia, DF - Brazil

^[2] Fed Inst Rondonia, BR-76820441 Porto Velho, RO - Brazil

^[3] Anhui Univ, Sch Chem & Chem Engn, Hefei 230601, Anhui - Peoples R China

• Document type: Journal article
• Source: AIP ADVANCES; v. 8, n. 5 MAY 2018.
• Web of Science Citations: 15

Abstract

This study reports on the synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles (NPs) synthesized by chemical co-precipitation in alkaline medium at increasing temperatures in the range of 27 degrees C to 100 degrees C. High-quality samples in the size range of 5 to 10 nm were produced using very low stirring speed (250 rpm) and moderate alkaline aqueous solution concentration (4.8 mol/L). Three samples were synthesized and characterized by x-ray diffraction (XRD) and room-temperature (RT) magnetization measurements. All samples present superparamagnetic (SPM) behavior at RT and Rietveld refinements confirm the inverse cubic spinel structure (space group Fd-3m (227)) with minor detectable impurity phase. As the synthesis temperature increases, structural parameters such as lattice constant and grain size change monotonically from 8.385 to 8.383 angstrom and from 5.8 to 7.4 nm, respectively. Likewise, as the synthesis temperature increases the NPs' magnetic moment and saturation magnetization increases monotonically from 2.6 x 10(3) to 16 x 10(3) mu(B) and from 37 to 66 emu/g, respectively. The RT magnetization (M) versus applied field (H) curves were analyzed by the first-order Langevin function averaged out by a lognormal distribution function of magnetic moments. The excellent curve-fitting of the M versus H data is credited to a reduced particle-particle interaction due to both the SPM behavior and the existence of a surface amorphous shell layer (dead layer), the latter reducing systematically as the synthesis temperature increases. (c) 2017 Author(s). (AU)

• FAPESP's process: 09/54082-2 - Acquisition of a vibranting sample magnetometer coupled with a superconducting quantum interference device assensor (Squid-VSM) with cryogenic closed cycle
• Grantee: Ernesto Chaves Pereira de Souza
• Support Opportunities: Multi-user Equipment Program