Exchange Bias Effect Of Manganese Oxides Nanoparticle

The exchange bias effect of magnetic nanoparticles is a intensive field in spintronics. It is important to study the exchange bias effect of magnetic nanoparticles for beating the superparamagnetic limit with exchange bias effect. It will lie the foundations of developing practical applications of spintronic devices. In this thesis, we choose single phase MnO nanoparticls and core-shell MnO/Mn3O4. We measure the magnetic single phase MnO nanoparticls and core-shell MnO/Mn3O4with X-ray diffractions (XRD), Transmission Electronic Micrograph (TEM), high-resolution Transmission Electronic Micrograph (HRTEM), Magnetic Properties Measurement system (MPMS) and Physical Properties Measurement system (PPMS).(l)First, we have synthesized Mn-Oleate using Sodium Oleate and MnCl2. We have synthesized single phase MnO nanoparticles with Mn-Oleate,1-octadecene, Oleic Acid and fine MnO nanoparticles with vacuum and protecting by inert gas. We have measured the MnO nanoparticles with XRD, TEM and HRTEM. The XRD patterns and the TEM photograph shows that we have synthesized fine MnO nanoparticles. We also have measured the exchange bias effect of single phase MnO nanoparticles. We have exhaustively studied the phase and nanostructure of MnO nanoparticles with exchange bias effect and HRTEM. We guess that spin glass formed at the surface of the MnO nanoparticles. We find the evidence that spin glass formed at the surface of the MnO nanoparticles by the AC susceptibility.(2)We have synthesized core-shell MnO/Mn3O4nanoparticles with the oxidation of single phase MnO nanoparticles in situ by adding in weak oxidant trimethylamine N-oxide dihydrate (TMNO). We have measured the core-shell MnO/Mn3O4nanoparticles oxidized MnO nanoparticles at different temperature. We have found that the oxidation of particle occurs from the surface inward with the increase of oxidation temperature, MnO nanoparticle were oxidized to Mn3O4nanoparticles with increasing temperature and finally Mn3O4nanoparticles formed. We have tuning the exchange bias effect by the measurement of exchange bias. The exchange bias field increases first and then decreases with increasing oxidation temperature, and we have studied the maximum of the exchange bias field. We study the relation between the exchange bias field and cooling field of core-shell MnO/Mn3O4nanoparticles comparing to single phase MnO nanoparticles. We also studied the training effect of both single and core-shell nanoparticles.