Distinguishing nanostructured Al-doped maghemite-like Fe2-yAlyO3 from spinel-like Fe3-yAlyO4

CABRERA, A. F.; RODRÍGUEZ TORRES, C. E.; STEWART, SILVANA J.

Hyperfine Interactions

Springer

Año: 2024 vol. 245

Wepresentaninvestigationof a nanostructured Fe-Al-O systemwith x=Al/Al + Fe ratios of 0.17, 0.33 and 0.50, prepared by theautocombustionmethod.Themainphasefoundinallsamplesisthecubic spinelphase.Theinclusion ofAlinthespinelstructure resulted ina progressive decrease inboth thecellparameter and the grain size, with the former approaching thecellparameterof maghemite rather than magnetite. Although the XRD patterns match those reported for AlFe2O4, Mössbauer spectroscopy and magnetic measurementsallows us to determine that the formedspinel phasecanbe identified as Aldoped maghemite-like Fe2-yAlyO3. The room temperature Mössbauer spectrum of sample x=0.17 consists of magnetic componentsbelonging to iron at theiron(III)oxide spinel sites, plus a central doublet. For higher Al content, the relative area of the magneticcomponentsdecreases, and the spectra mainly consists of a Fe3+ broad doublet corresponding to superparamagnetic iron(III) oxide particles.The13Kspectrum ofx=0.33sample(nominally AlFe2O4) is mainly composed of magnetic sites belonging to blocked particle moments of Al-doped maghemite-like particles. The magnetization loops are consistent with a ferro/ferrimagnetic behaviour, whose saturation magnetization decreases with the incorporation of Al.