We report magnetic properties and magnetic relaxation phenomena in a sample comprised of nanocrystalline ${\mathrm{CoFe}}_2$${\mathrm{O}}_4$ (∼97%)+γ-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ (∼3%) and polymer in potassium silicate (as magnetic glass) nanoparticle systems in which two very different barrier distributions contributed to the relaxation behavior. We have demonstrated experimentally that only energy barrier distributions and the thermal activation process could not account for a plateau in the viscosity data at low temperatures. Quantum tunneling of magnetization is suggested below ∼3 K. © 1996 The American Physical Society.

• Received 1 March 1996

DOI:https://doi.org/10.1103/PhysRevB.54.4101