I.K. Pour, D.J. Krajnovich, et al.
SPIE Optical Materials for High Average Power Lasers 1992
We study the magnetic properties of dispersions of uniformly sized, chemically synthesized cobalt nanoparticles (NP's), observing a crossover from a blocked state to a superparamagnetic one with increasing temperature. By analyzing magnetization data, we determine the distributions of NP volumes and anisotropies, and establish that variations in the shapes of the magnetic cores of the NP's generate the anisotropy governing the crossover. We characterize the frustrated low-temperature state produced by the competition between dipolar interactions and anisotropy at sufficiently high NP density through remanent magnetization measurements, and explain the results through analysis of a simple model.
I.K. Pour, D.J. Krajnovich, et al.
SPIE Optical Materials for High Average Power Lasers 1992
Frank R. Libsch, Takatoshi Tsujimura
Active Matrix Liquid Crystal Displays Technology and Applications 1997
Arvind Kumar, Jeffrey J. Welser, et al.
MRS Spring 2000
Ranulfo Allen, John Baglin, et al.
J. Photopolym. Sci. Tech.