Large coercivity and low-temperature magnetic reorientation in ε-Fe2O3 nanoparticles -: art. no. 044307

A large coercive field, H-C=20 kOe, is obtained at room temperature in epsilon-Fe2O3 nanoparticles embedded in a silica matrix, produced by sol-gel chemistry. The combination of a relatively high magnetic anisotropy together with the small saturation magnetization are responsible for this large H-C. Upon cooling, a strong reduction of H-C is observed at T similar to 100 K, which is accompanied by a drastic reduction of the squareness ratio M-R/M-S. Neutron-diffraction measurements reveal the existence of a low-temperature magnetic transition to which the softening of this material can be ascribed. (c) 2005 American Institute of Physics.