Structural, fluorescence and magnetic properties of Cr3+ cation substituted of Co0.7Mn0.3CrxFe2-xO4 (0 ≤ x ≤ 1) nanoparticles

A series of Cr-substituted Co_0.7Mn_0.3Cr_xFe_2-xO₄ nanoparticles for (0.0 ≤ × ≤ 1; increment of 0.2), have been fabricated utilizing sol–gel self-ignition route, samples were calcinated for six h at 800 ˚C. XRD performed the structural characteristics, and the results support the shaping of cubic spinel structure with space group Fd-3m for the samples with a significant ratio of hematite decreases gradually with increasing Cr concentration. Moreover, substituting Cr³⁺ ions caused a significant reduction in crystallite size (44.75–28.65 nm) by increasing Cr³⁺ ions concentrations. According to the FTIR spectrum, the metal–oxygen bond bands have shifted towards higher wavelengths, these absorption bands indicated the spinel structure formation having two sub-lattices: tetrahedral (A) and octahedral (B) sites. The lowest frequency band υ₂ was assigned to octahedral M–O and the highest frequency band υ₁ was set to stretch vibrations of tetrahedral M–O. HR-TEM image results revealed that all samples show well-crystallized nanoparticles with soft accumulation, which may be due to their higher calcination and the magnetic particles' interactions. The particle size decreases from 62.59 to 44.17 nm confirming the decrease occurred in XRD. A study of magnetic properties explained that saturation magnetization decreases from 67.90 to 10.50 emu/g. These materials have low coercivity and small squareness values make them suitable options for medication delivery and contrast agents in magnetic fluids and magnetic resonance imaging. Strong and sharp red emission at 600 nm and weak UV emissions at 324 nm are obtained from the fluorescence spectra. The Cr substitution enhances the red emission, which has a maximum intensity obtained for X = 0.4, indicating fewer defects in the matrix due to the Cr replacement. The obtained effect of Cr content on structural, spectral and magnetic properties of Co_0.7Mn_0.3Cr_xFe_2-xO₄ can be candidate it for the future miniaturizing of ferroelectric and integrated electrooptic device applications.