Abstract
1Department of Mechanical and Chemical Engineering, North Carolina A&T State University, Greensboro, NC 27411, USA
2Department of Mechanical and Chemical Engineering, North Carolina State University, Raleigh, NC 27495, USA
3Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
A pulsed laser deposition technique has been used to synthesize a uniform distribution of Ni nanoparticles
of controllable size in Al2O3 thin film matrix. The ability to control particle size in confined layers
provides a very convenient means to tune the magnetic properties from superparamagnetic to ferromagnetic.
The coercivity of these particles was measured at various temperatures as a function
of particle size. The results indicate that the magnetic transition from single- to multi-domain region
occurs at a larger particle size at higher temperature than at lower temperature. Stronger magnetic
interaction amongpar ticles at lower temperatures is believed to lead to the formation of smaller sized
domains for any given particle size in order to minimize the interaction energy.