Magnetic and Structural Properties of Nanoparticles

Magnetic properties of NiO nanoparticles prepared by the sol-gel method in the size range D=5 nm to 20 nm, with and without oleic acid coating, are reported. For the coated and uncoated NiO nanorods of 5 nm diameter, variations of the magnetization M with temperature T (5 K to 370 K) and temperature variations of the EMR (electron magnetic resonance) spectra were measured to determine the respective blocking temperatures. For all the particles, measurements of M versus T in the zero-field cooled (ZFC) and field-cooled (FC) modes are used to determine the average blocking temperature Tp. For the OA coated particle, Tp increases with increase in size D as expected for superparamagnetic particles. However for the uncoated NP, Tp decreases initially with increase in size for D 10 nm, but for D 10 nm, Tp follows the same trend as for the coated NP. These differences are interpreted in terms of significant interparticle interaction.

Autorentext

LG Electronics (Apr. 2008 ~ present); Solar Energy Massachusetts Institute of Technology, Cambridge,Massachusetts USA, Francis Bitter Magnet laboratory, Post-Doctoral Associate West Virginia University, Morgantown, West Virginia USA, Ph.D. Physics (Aug. 2001 ~ Jun. 2006)