Charge transfer induced magnetism in sol–gel derived nanocrystalline BaTiO3

• The magnetism in nc-BTO is explained qualitatively by the modified Stoner criterion.
• The TEM study reveals the structural information at the grain boundary.
• The conductivity studies clearly show a behaviour similar to doped materials.
• The optical studies prove the existence of charge transfer in this material.

Nanocrystalline BaTiO3 is prepared by sol–gel synthesis. The charge transfer and different state mixing effects are used in explaining the observed magnetism by the modified Stoner theory. The magnetic coercivity is found to decrease from 125 to 43 Oe as temperature increases from 5 K to 300 K. The optical absorption shows band narrowing arising from exchange–correlation and many-body effects of free carriers created on the surface of nanoparticles, as supported also by the non-adiabatic small polaron conductivity derived from impedance spectroscopy.