Structural and Mössbauer studies of nanocrystalline Mn2+-doped Fe3O4 particles

K. S. Al-Rashdi, H. M. Widatallah, F. Al Ma’Mari, O. Cespedes, M. Elzain, A. Al-Rawas, A. Gismelseed, A. Yousif

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Nanocrystalline Mn2+-doped magnetite (Fe3O4) particles of the composition MnxFe3−yO4(x=0.0,0.1,0.2,0.3,0.4and0.5;y=2x3), prepared using chemical precipitation under reflux with the Mn2+ ions substituting for Fe3+ ions rather than Fe2+ ones, are characterized mainly with XRD and 57Fe Mössbauer spectroscopy. All samples were found to have spinel-related structures with average lattice parameters that increase linearly with the Mn2+ concentration, x. The particle size for the samples varied from ∼8 nm to 23 nm. The oxidation of Fe2+ to Fe3+ at surface layers of the Fe3O4 nanoparticles leading to the formation of maghemite (γ-Fe2O3) was found to considerably weaken with increasing Mn2+ concentration. The percentage of the nanoparticles that exhibit short range magnetic ordering due to cationic clustering and/or superparamagnetism increases from 17% to 32% with increasing x. The dependence of isomer shifts of the 57Fe nuclei at the tetrahedral and octahedral sites on dopant Mn2+ concentration is emphasized. The electric quadrupole shifts indicate that the MnxFe3−yO4 particles undergo Verwey transition. The effective hyperfine magnetic fields at both crystallographic sites decrease with increasing Mn2+ concentration reflecting a size effect as well as a weakening in the magnetic super-exchange interaction. The Mössbauer data indicate that for x ≤ 0.2, the dopant Mn2+ ions substitute solely for octahedral Fe3+ ions whereas for x > 0.2 they substitute for Fe3+ at both tetrahedral and octahedral sites.

Original languageEnglish
Article number3
JournalHyperfine Interactions
Volume239
Issue number1
DOIs
Publication statusPublished - Dec 1 2018

Keywords

  • Defects
  • Doping
  • Maghemite
  • Magnetite
  • Mössbauer spectroscopy
  • Nanocrystalline particles
  • XRD

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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