MAGNETIC AND OPTICAL-PROPERTIES OF GAMMA-FE2O3 NANOCRYSTALS

Gamma-Fe2O3 nanocrystals have been synthesized in a polymer matrix by an ion exchange and precipitation reaction. The particles are crystall ine with a mean diameter of 85 angstrom. The unit cell volume is 1735. 2 angstrom3 corresponding to a unit cell compression of 0.35%. Magneti zation and susceptibility data from experiment and computer simulation s indicate that the system is superparamagnetic. The calculated magnet ic anisotropy for the particles is two orders of magnitude larger than that of bulk gamma-Fe2O3. The optical absorption edge is red shifted with respect to that of an epitaxially grown single-crystal film of ga mma-Fe2O3. The red shift is attributed to lattice strain in the small particles.