Tuning the magnetic properties of hard–soft Ba_0.5Sr_0.5Fe₁₀Al₂O₁₉ and Ni_0.1Co_0.9Fe₂O₄ nanocomposites via one pot sol–gel auto combustion method for permanent magnet applications

Abstract

Permanent magnets generate magnetic fields that can be sustained when a reverse field is supplied. These permanent magnets are effective in a wide range of applications. However, strategic rare-earth element demand has increased interest in replacing them with huge energy product (BH)max. Exchange-coupled hard/soft ferrite nanocomposites have the potential to replace a portion of extravagant rare earth element-based magnets. In the present, we have reported the facile auto-combustion synthesis of exchange coupled Ba0.5Sr0.5Fe10Al2O19 and Ni0.1Co0.9Fe2O4 nanocomposites by increasing the content of soft ferrite over the hard from x= 0.1 to 0.4 wt.%. The XRD combined with Rietveld analysis reflected the presence of hexaferrite and spinel ferrite without the existence of secondary phases. The absorption bands from the FTIR analysis proved that the presence of M-O bonds in tetrahedral site and octahedral sites. Rod and Non-spherical images from TEM represent the hexaferrite and spinel ferrite. Smooth M-H curve and single peak of SFD curve proves that the material has undergone a good exchange coupling. The nano powders displayed an increase in saturation magnetization and decrease in coercivity with the increases in the spinel content. The prepared nano composites were showing higher energy product. And the composite with the ratio x=0.2 displayed a higher value of (BH)max of 13.16 kJ/m3.