Exchange bias effect in nickel zinc ferrite–mesoporous silica nanocomposites

Nickel zinc ferrite–mesoporous silica nanocomposite (NZF–MS) was synthesized using impregnation method. The microstructure was investigated by transmission electron microscopy. A magnetic exchange bias effect was exhibited by the nanocomposites. This was ascribed to the presence of a ferromagnetic core and antiferromagnetic shell structure. Electron microscopic studies confirmed the presence of a core–shell structure with NZF forming the core. The zero-field cooled magnetization data as a function of temperature indicated the presence of an antiferromagnetic phase which is believed to be formed by the diffusion of Fe3+ or Ni2+ ions into the silica glass.