Cation distribution in MFe2O4 (M = Ni, Co): X-ray diffraction, electron spectroscopy, Raman, and magnetization studies

We report the structural, vibrational, surface composition, and magnetic properties of as-prepared and annealed (600–1200 °C) MFe 2 O 4 (M = Ni, Co) samples to investigate the cation distribution. Rietveld refinement of X-ray diffraction data indicated a spinel structure for all samples. Raman and X-ray photoelectron analyses suggest the presence of an inverse spinel structure in the samples. Furthermore, the mixed valence states (Fe 2+ , Fe 3+ , Ni 2+ /Co 2+ ) of the cations and their occupancies over tetrahedral and octahedral sites have been evaluated. We have noticed a systematic increase in saturation magnetization (M S ) (10.7–43.5 emu/g for NiFe 2 O 4 , 36.1–83 emu/g for CoFe 2 O 4 ) with increasing annealing temperature up to 1000 °C, and then M S slightly decreased for the samples annealed at 1200 °C. Furthermore, the values of coercivity (H C ) varied over the ranges 15–125 Oe for NiFe 2 O 4 and 300–1644 Oe for CoFe 2 O 4 , suggesting that these materials are promising candidates for biomedical and high-frequency applications. • Structural and magnetic properties of NiFe 2 O 4 and CoFe 2 O 4 investigated to study the cationic distribution. • Raman analysis revealed the formation of inverse spinel structure in samples. • CFO showed enhanced magnetization (36.1–83 emu/g) compared with NFO (10.7–43.5 emu/g). • XPS revealed the mixed valence states (Fe 2+ , Fe 3+ , Ni 2+ /Co 2+ ) of cations and their occupancies over tetrahedral and octahedral sites.