Magnetic properties of spinel ferrites and M-type hexaferrites for permanent magnet applications

Abstract

Permanent magnet materials have attracted a lot of interest of researchers worldwide because of their use in many technological and industrial applications. The largest market of permanent magnets is essentially made up of rare-earth based magnets or ferrites magnets. However, it should be noticed that each permanent magnet application is particular and responds to specific needs and therefore to different conditions. The present thesis work was focused on Cobalt spinel ferrites CoFe2O4 and M-type Strontium hexaferrites SrFe12O19 by studying their structural, electronic, and magnetic properties using a combination of theoretical and experimental investigations. Our theoretical results based on density functional theory and Monte Carlo simulation showed the strong dependence of the magnetic properties of Cobalt spinel nanoferrites to the nanoparticles size and we extracted a theoretical value of the maximum energy product (BH)max of about 2.83 MG.Oe for cubic-shaped CoFe2O4 nanoparticles with an average particle size of 21 nm. A possibility of the improvement of the maximum energy product (BH)max of M-type Strontium hexaferrites has been proved experimentally by varying the synthesis methods and through the preparation of hard/soft nanocomposites with the presence of the exchange coupling behavior.