Magnetic properties of nanoscale crystalline maghemite obtained by a new synthetic route

• Published in: Journal of magnetism and magnetic materials Vol. 324; no. 19; pp. 3029 - 3033
• Main Authors: Mercante, L.A., Melo, W.W.M., Granada, M., Troiani, H.E., Macedo, W.A.A., Ardison, J.D., Vaz, M.G.F., Novak, M.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2012; Elsevier
• Subjects: Anisotropy; Co-precipitation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Coprecipitation; Cross-disciplinary physics: materials science; rheology; Dipolar interaction; Exact sciences and technology; Magnetic material; Magnetic permeability; Magnetic properties; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetically ordered materials: other intrinsic properties; Materials science; Mössbauer effect; other γ-ray spectroscopy; Nanocrystalline materials; Nanomagnetism; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Physics; Saturation moments and magnetic susceptibilities; Triethylamine; Dipolar interaction; Magnetic material; Co-precipitation; Nanomagnetism; Temperature dependence; Moessbauer effect; Iron oxide; Dipole interactions; Energy barrier; Magnetic susceptibility; Nanoparticles; Relaxation; Transmission electron microscopy; Anisotropy; Chemical preparation; Arrhenius equation; Magnetic materials; Nanostructured materials; Coprecipitation; Nanocrystal; Magnetic properties
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2012.04.049

In this work we describe the synthesis and characterization of maghemite nanoparticles obtained by a new synthetic route. The material was synthesized using triethylamine as a coprecipitation agent in the presence of the organic ligand N,N′-bis(3,5-di-tert-butyl-catechol)-2,4-diaminotoluene (LCH3). Mössbauer spectrum at 4K shows typical hyperfine parameters of maghemite and Transmission Electron Microscopy images reveal that the nanoparticles have a mean diameter of 3.9nm and a narrow size distribution. AC magnetic susceptibility in zero field presents an Arrhenius behavior with unreasonable relaxation parameters due to the strong influence of dipolar interaction. In contrast when the measurements are performed in a 1kOe field, the effect of dipolar interactions becomes negligible and the obtained parameters are in good agreement with the static magnetic properties. The dynamic energy barrier obtained from the AC susceptibility results is larger than the expected from the average size observed by HRTEM results, evidencing the strong influence of the surface contribution to the anisotropy. ► Maghemite nanoparticles obtained by a new synthetic route. ► TEM images shown crystalline nanoparticles with average 3.9nm diameter. ► Normal Arrhenius behavior restored with applied DC fields.