Magnetic behavior of La-doped Fe3O4 studied by perturbed angular correlation spectroscopy with 111Cd and 140Ce

• Published in: Journal of applied physics 2015-05, Vol.117 (17)
• Main Authors: Matos, I. T., Bosch-Santos, B., Cabrera-Pasca, G. A., Carbonari, A. W.
• Format: Article
• Language: English
• Subjects: Angular correlation; Bulk sampling; Correlation analysis; Curie temperature; Hyperfine structure; Iron oxides; Magnetic dipoles; Magnetic properties; Magnetism; Nanoparticles; Nuclei; Order disorder; Spectrum analysis; Temperature dependence
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4916023

In this paper, the local magnetic properties of La-doped Fe3O4 (5% and 10%) bulk and Nanoparticles (NPs) samples were studied by measuring hyperfine interactions in a wide range of temperature from 10 to 900 K with perturbed γ-γ angular correlation spectroscopy using 111In(111Cd) and 140La(140Ce) as probe nuclei. Results for the temperature dependence of the magnetic hyperfine field (Bhf) for bulk and NP samples, pure and doped with La show that its behavior follows a second order Brillouin-like transition from which the Curie temperature (TC) was determined (TC ∼ 855 K). Results also show two different regions in NP samples: the core where a minor fraction of probe nuclei with well defined magnetic dipole frequency was observed and the shell where a major fraction with broad distributed electric quadrupolar frequency (surface effect in NP) was observed. The Verwey transition TV ∼ 120 K, due the order disorder phase, was also observed in all samples. The results are discussed in terms of the magnetic exchange interaction between Fe2+ and Fe3+ ions in the two regions of NP.