Coercivity of nanoporous Ni produced by dealloying

Nanoporous Ni specimens with the ligament lengths of 10-210 nm were produced by the dealloying of Ni(0.25)Mn(0.75) alloy and annealing at 473-873 K. The coercivity (H(c)) increased with increasing ligament length (L) up to 50 nm, and decreased with increasing L above 50 nm. At L < 50 nm, the size dependence of H(c) for nanoporous Ni is lower than that for nanocrystalline Ni. The low size dependence of H(c) is discussed on basis of a random anisotropy model.