Magnetic and optical properties of γ-Fe2O3 nanocrystals

Abstract

γ‐Fe₂O₃ nanocrystals have been synthesized in a polymer matrix by an ion exchange and precipitation reaction. The particles are crystalline with a mean diameter of 85 Å. The unit cell volume is 1735.2 ų corresponding to a unit cell compression of 0.35%. Magnetization and susceptibility data from experiment and computer simulations indicate that the system is superparamagnetic. The calculated magnetic anisotropy for the particles is two orders of magnitude larger than that of bulk γ‐Fe₂O₃ . The optical absorption edge is red shifted with respect to that of an epitaxially grown single‐crystal film of γ‐Fe₂O₃ . The red shift is attributed to lattice strain in the small particles.