Magnetic properties of Fe deposited into anodic aluminum oxide pores as a function of particle size

A combination of magnetic and electron microscopic measurements on iron deposited in chemically widened anodic aluminum oxide films has allowed us to relate the coercivity of these materials to the dimensions of the metal particles. The coercivity is found to be highly anisotropic and to depend on the aspect ratio of the metallic particles. The functional dependence of Hc on the aspect ratio fits the expression reported by Jacobs and Bean [Phys. Rev. 100, 1060 (1955)] for magnetization reversal by symmetric fanning. This is likely due to the fact that in our unannealed samples the metal deposit consists of a cylindrical assembly of fused single-domain particles. Pore widening by chemical dissolution of the anodic oxide is found to depend quadratically on the time that the sample is soaked in the acid bath.