Disk having an underlayer that includes a plurality of nonmagnetic layers interleaved with magnetic layers

A magnetic disk comprising:

• a substrate;
• a soft magnetic underlayer disposed over the substrate, the underlayer including a plurality of magnetic layers each containing a FeCoN alloy consisting of iron, cobalt, and nitrogen, and having an atomic concentration of iron that is greater than an atomic concentration of cobalt, and having an atomic concentration of nitrogen that is less than the atomic concentration of cobalt, the atomic concentration of nitrogen being greater than zero and less than eight percent, the underlayer including a plurality of nonmagnetic layers that are interleaved with the magnetic layers, each of the nonmagnetic layers having a thickness that is less than one-tenth that of an adjoining layer of the magnetic layers;
• and
• a media layer disposed over the underlayer and containing a magnetically hard material having an easy axis of magnetization oriented substantially perpendicular to both the media layer and the underlayer.