Cobalt doping on nickel ferrite nanocrystals enhances the micro-structural and magnetic properties: Shows a correlation between them
JOURNAL OF ALLOYS AND COMPOUNDS
Authors: Debnath, Simi; Das, Ratan
Abstract
In this paper, PVP capped nickel ferrite nanocrystals (NFN) and cobalt doped nickel ferrite nanocrystals (CNFN) have been prepared by thermal heat treatment method, followed by sintering at 700 degrees C. The synthesized nanocrystals have been analysed through XRD, TEM and SEM for their structural and morphological study. XRD analysis confirms the crystalline nature with cubic FCC lattice structure, whereas TEM and SEM study reveals the spherical morphology of the prepared nanocrystals with approximate average size of 21 nm and 24 nm for NFN and CNFN respectively. Also, the EDX spectra further confirms the incorporation of Co in the nickel ferrite nanocrystals (NFN) after doping. Further, Nelson-Riley plot has been used by considering error function to calculate the cubic lattice constant values and that are obtained as 0.835 nm and 0.841 nm respectively for NFN and CNFN. Most importantly, doping effect on microstructural properties have been analysed by considering Williamson-Hall (W-H) and Size-Strain Plot (SSP) method, and all these are then compared with that obtained from Halder-Wagner Method (H-W). Calculated average particle size from W-H, SSP and H-W method are found to match very well with that obtained from TEM and SEM analysis. Finally, magnetic parameters of NFN and CNFN have been studied by vibrating-sample magnetometer (VSM), where increase in saturation magnetization (Ms) from 19.97 emu/g to 26.93 emu/g and coercivity (Hc) value to 307 Oe has been observed with Co doping in NFN. The increase of such parameters has further been explained in terms of super exchange interaction between magnetic ions, total magnetic moments and magneto-crystalline anisotropic property, along with decrease in surface spin disorder and spin canting effect. Finally, a correlation between microstructural properties and magnetic properties has been observed. Such a good magnetic material (CNFN) may be used for the application of memory devices, magnetic recording media, and as good adsorbent for toxic materials like different dyes in water. (C) 2020 Elsevier B.V. All rights reserved.
A new strategy for simultaneously enhancing nonlinear optical response and electron stability in novel cup-saucer(+)-cage(-)-shaped sandwich electride molecules with an excess electron protected inside the cage
DALTON TRANSACTIONS
Authors: Wang, Jia-Jun; Zhou, Zhong-Jun; Bai, Yang; He, Hui-Min; Wu, Di; Li, Ying; Li, Zhi-Ru; Zhang, Hong-Xing
Abstract
Novel cup-saucer-cage-shaped sandwich electride molecules calix[4]pyrrole center dot center dot center dot K3O+center dot center dot center dot e@CnFn-, (n = 8, 10, 14, 20, and 36) with an excess electron protected inside the CnFn cage are constructed theoretically. In the sandwich structures, the below calix[ 4] pyrrole cup pushes the valence electron of the sandwiched superalkali atom K3O saucer, forming an excess electron, which is further pulled and protected inside the above CnFn cage, thus an electron-transfer relay occurs. In particular, owing to the unusual electron transfer, an unusual and fortunate phenomenon is discovered that increasing the CnFn cage size enhances not only the nonlinear optical response (beta(0)), but also the electron stability (VIP). Thus, a new strategy of simultaneously enhancing beta(0) and VIP values is found for the first time, namely by increasing the CnFn cage size in novel cup-saucer-cage-shaped sandwich electride molecules, with the excess electron protected inside the cage.