57Fe-Mössbauer studies of the CuxFe3−xO4 spinel system

Abstract

Mössbauer spectroscopy has been used to examine the effect of increasing copper ion concentration on the iron distribution in CuxFe3−xO4(0⩽x⩽0.9). For x⩽0.37, fast electron exchange among octahedral iron ions occurs as in Fe3O4, suggesting that the itinerant electrons associated with the octahedral Fe2+ ions remain delocalized in the sublattice. At high values of x (x⩾0.59), however, the itinerant electrons become localized in a small fraction of exchange-coupled iron ions. The relative numbers of distinguishable cations making up the complements of the octahedral sites of the copper ferrites are determined.

Superparamagnetic transition and local disorder in CuFe2O4 nanoparticles

“…A third sextet is observed, centered at a lower field of H3=46.2 T and asymmetrically broadened, indicating a distribution of hyperfine fields. This may be due to the formation of the solid solution Cu x Fe 3-x O 4 with an extended range of x, where the different Fe 3+ environments result in the observed hyperfine field distribution (22).…”

Reversibility of the synthesis-decomposition reaction in the ball-milled Cu-Fe-O system

“…The small hyperfine field and broad lines are related to sample regions with oxygen vacancies and/or high local disorder produced during milling. We associate these features with the formation of sample regions with Cu x Fe 3−x O y stoichiometry (see discussion below) [21].…”

Mössbauer Spectroscopy Applied to Inorganic Chemistry

“…Other authors also have suggested the simultaneous appearance of octahedral Fe 2 .5+ and Fe3+ subpatterns, the latter one arising from ferric ions that do not participate in the charge transfer and therefore being unresolved from the A-site component. [385][386][387][388] Commonly, these conclusions were arrived at on the basis of the observation that the area ratio SAl SB is considerably different from the value expected from the known cation distribution. Clear-cut evidence that unpaired Fe 3 + ions on octahedral sites of substituted magnetites indeed do exist was provided by high-field M6ssbauer measurements on nonstoichiometric Fe304/76,389 on COXFe3_X04,390 and on Lio.5(1_X)Fe2.5+0.5X04,391 in which cases an additional four-line pattern, with parameters typical for Fe~+, has to be included in the fit.…”

“…AI20 3,381,383,386,387,389f FeAl20 4,87 FeB,276 Fe3B,21Of Fe7J324,208 FesoB20,190,273 FexB100' 276f Subject Index FeB03,255,257,267f FeSlB\3.5Si3.5CZ,192f,207f Fe3C,211,34lf Fe5CZ,34lf FesoCzo,273 FeCoCr04,99 Fe70C07oM030Si3oB30,272 Fe5C055Nizo(SiBho,272 FeCoZ0 4,78 FeZ.97C00.Q304,74 (Feo.zCOO.8)801'17AI3,204 FeCoSiB,276 (Fel_zCozhSiB,282 (Fel_zCozhSiB,282 FexC07S_xSi9B13,276,279 Fe4C074Si9B13,282 Fe5SCozoSi9Bl3,279 FeCrZ04,86,92,105,113 FeZCr04,93 Fe I.5Cr 1.5°4,289 FeGez,471 FesoGezo,273 Fez.4z5Lio.5z5Sllo.0504,…”