Examining the structural, magnetic and dielectric properties of exchange spring nanocomposite magnets comprising Ba0.5Sr0.5Fe12O19 and Zn0.5Co0.5Fe2O4

Abstract

Exchange-coupled hard/soft ferrite nanoparticles are prospective to squeeze out a part of expensive magnets based on rare earth elements. However, the known exchange-coupled composite ferrite nanoparticles often suffer from the lack of a powerful hard core, high defective synthesis of magnetic phases and a poor interface between them. This work is featured by the use of highly coercive Ba0.5Sr0.5Fe12O19 magnets prepared by sol–gel combustion. Here in we demonstrate the synthesis of magnetic nanocomposites comprising Ba0.5Sr0.5Fe12O19 and Zn0.5Co0.5Fe2O4 hard/ soft ferrites by gradually increasing the share of spinel ferrites in the hard ferrites. Four samples of nanocomposites were prepared with the increasing order of hard ferrites using simple solgel auto-combustion method. Thermal breakdown examinations have been performed using TGA/DSC on the as-synthesised material from 0 °C to 1250 °C, and the temperature stability of the sample was detailed. The XRD analyses proved the presence of hexagonal and cubic crystal structure in each nanocomposite. Transmission Electron Microscopy was used to examine the morphology and topology of the nanocomposites. Hard and soft ferrites were detected in rod and non-spherical microstructures, correspondingly. The bending and the stretching vibrations in the sample was studied by using Fourier Transform Spectroscopy. The magnetic response of the synthesised samples was studied by using the Vibrating Sample Magnetometry. The prepared Nano powders displayed a highest coercivity Hc of 6307 Oe for pure hard ferrite while the pure spinel ferrite displayed a coercivity of 80 Oe. All the synthesized samples showed smooth M−H curves and single peak on dM/dH against H curves this indicates that complete exchange-coupled effects between the phases are achieved. The saturation magnetization increased with the increase in the content of spinel ferrite whereas the coercivity decreased with the increase in the spinel content.