Embodiments of the present invention provide a magnetic disk drive capable of allowing higher data transfer rates and higher recording densities. According to one embodiment, an upper
magnetic core and lower
magnetic core comprise a multi-layered magnetic film formed by alternately stacking a face-centered cubic (fcc) crystalline magnetic
thin layer and a body-centered cubic (bcc) crystalline magnetic
thin layer by plating. The plating bath is such that the temperature is about 30±1° C., pH is about 2.0−1.0 to 2.0+0.5,
metal ion concentrations are about 5 to 25 (g / l) for Ni2+ and 5 to 15 (g / l) for Fe2+,
saccharin sodium concentration is about 1.5±1.0 (g / l),
sodium chloride concentration is about 25±5 (g / l), and
boric acid concentration is about 25±5 (g / l). Since each layer's
crystal structure is different from that of its adjacent lower layer, epitaxial growth is broken within each layer. Thus, since
crystal grains are reduced in size, it is possible to lessen the decrease of the permeability μ at higher frequencies.