Biosynthesis effect of Moringa oleifera leaf extract on structural and magnetic properties of Zn doped Ca-Mg nano-spinel ferrites

Abstract ZnxCa0.5-x/2Mg0.5-x/2Fe2O4 (x = 0.0–0.6) nano-spinel ferrite (NSFs) were prepared by ultrasonic irradiation with Moringa oleifera leaf extract (group A) and without Moringa oleifera leaf extract (group B). The synthesis done with Moringa oleifera leaf extract is green synthesis. The structure and morphologies of both group A and B NSFs were investigated by XRD, SEM, TEM, and FT-IR in details. The crystallite sizes of group A and B products were calculated as within the range of 11–17 nm and 16–28 nm, respectively. The magnetic features of different nanoparticles of group A and B NSFs have been investigated at room (T = 300 K) and low (T = 10 K) temperatures by means of a vibrating sample magnetometer (VSM). All samples displayed superparamagnetic (SPM) behavior at room temperature, with no or negligible coercivity and retentivity. Nevertheless, the different samples revealed opened M−H hysteresis loops at a temperature of 10 K, which indicates their ferromagnetic (FM) behavior at very low temperatures. The various magnetic parameters including the saturation magnetization (Ms), remanent magnetization (Mr), squareness ratio (Mr/Ms), magneton number ( n B ), coercive field (Hc), etc. were extracted. The ZnxCa0.5-x/2Mg0.5-x/2Fe2O4 (x = 0.0 – 0.6) NSFs prepared using Moringa oleifera extract (Group A samples) displayed lower Ms values in comparison to NSFs prepared without using Moringa oleifera extract (Group B samples). Whereas, the coercivity is found to be larger in Group B samples than in Group A samples. These is mainly ascribed to the variations in particles size upon the use of Moringa oleifera extract. Compared to non-substituted Ca0.5Mg0.5Fe2O4 NSFs, it is noticed that the Ms value increases with Zn2+ ions substitution. The increase of Ms value is ascribed to the strengthening of exchange interactions and redistribution of cations (particularly Fe3+ ions) within the spinel lattice. At T = 10 K, the Hc value decreases with the rise of the Zn2+ content, which is attributed to the larger crystallites/particles that lead to the lower volume fraction of grains boundaries, which in turn conduce to less pinning of domain walls. The SQR values at 10 K for all NSFs of group A and B are between 0.2 and 0.3, which is below the theoretical limit of 0.5, reflecting the NPs consist of multi-magnetic domains. The obtained magnetic properties of group A NSFs are interesting, suggesting that this method could be considered as an alternative and effective green synthesis route with appropriate control of size, morphology, and physical features of magnetic nanoparticles.