Effects of porosity and pore orientation on the magnetization process were studied for lotus-type porous nickel and cobalt. It was confirmed that the saturation magnetization of porous metals varied linearly with the porosity, independent of the pore growth directions. Anisotropic behavior was clearly observed for the magnetization curves of lotus-type porous nickel, i.e., the magnetization perpendicular to the pore growth direction is always smaller than that parallel to the pore growth direction. The observed anisotropy is significantly large in the low magnetic field range below 2.5 kOe and is attributed to the anisotropic forms of the pores. Furthermore, it was found that the porosity dependence of magnetization at a certain applied field can be expressed by the empirical formula called Archie's law, and the values of their exponents in the parallel and perpendicular directions at around 200 Oe were determined to be 1.1 and 1.8, respectively. These values are coincident with those reported for electrical conductivity of lotus-type porous nickel in the parallel and perpendicular directions.
ASJC Scopus subject areas
- Physics and Astronomy(all)