Nanostructured metals exhibit unique magnetic properties,
such as superparamagnetism and low coercivity (Hc). Sun et al.
[82] reported that the np-Ni fabricated by etching NixCu1x
(x = 0.5–1) alloys exhibited enhanced Hc and reduced magnetic
anisotropy. The Hc of np-Ni films was enhanced with the decrease
of Ni content in the precursors due to reduced Ni ligament sizes. By
tuning the ligament size of np-Ni from 10 nm to 210 nm by annealing
at 473–873 K, Hakamada et al. [145] found that the Hc
increased first and then decreased with the ligament length
increasing, forming a volcano peak at the ligament size of 50 nm.
The critical size and Hc of np-Ni were much larger than those of
nanocrystalline Ni [146]. The evident enhancement of Hc might
be attributed to surface effect of non-collinear magnetism.