Magnetism in Non-Magnetic Materials

Abstract

The origin of magnetism in otherwise nonmagnetic materials sounds interesting. Prof. Sundaresan et al. have already shown that the ferromagnetism exists in nanoparticles of MgO, GaN, CdS, Al2O3, ZnO, CeO2, In2O3, SnO2, etc. due to defects on their surface. In this project, the main focus is on SiO2 & BaTiO3. SiO2 is the most abundant oxide on the earth and biocompatible as well so if we can induce magnetism in it; it can be extensively used (instead of other nonbiocompatible magnetic particles) in biomedical applications while BaTiO3 nanoparticles can also be used as vectors in nanomedicine. In this project, we have successfully synthesized BaTiO3 nanoparticles and different phases of SiO2 nanoparticles. Different characterizations such as SQUID, photoluminescence and small angle neutron scattering (SANS) were essential for understanding the origin of ferromagnetism. The highest magnetic moment obtained was 0.006 emu/g in both SiO2 & BaTiO3. SANS data of BaTiO3 shows that ferromagnetism indeed is coming from the surface oxygen vacancies. The reduction of magnetic moment after annealing in the air also shows that oxygen vacancies are primary source of ferromagnetism.