Magnetically soft, high saturation magnetization laminate of iron-cobalt-nitrogen and iron-nickel for perpendicular media underlayers
View Patent ↗A magnetic disk includes a substrate, a soft magnetic underlayer disposed over the substrate, and a media layer disposed over the underlayer. The underlayer includes a first plurality of layers each containing NiFe having an atomic concentration of iron that is at least about thirty percent. The underlayer further includes a second plurality of layers that is interleaved with the first plurality of layers. The second plurality of layers each contain FeCoN 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 is less than eight percent. The media layer contains a magnetically hard material having an easy axis of magnetization oriented substantially perpendicular to both the media layer and the underlayer.
1. A magnetic disk comprising:
a substrate;
a soft magnetic underlayer disposed over the substrate, the underlayer including a first plurality of layers each containing NiFe having an atomic concentration of iron that is at least about thirty percent, and a second plurality of layers that is interleaved with the first plurality of layers, the second plurality of layers each containing FeCoN 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 less than eight percent; 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.
2. The disk of claim 1 , wherein each of the layers containing FeCoN is more than ten times thicker than each of the layers containing NiFe.
3. The disk of claim 1 , wherein at least one of the layers containing FeCoN has a thickness that is less than thirty angstroms, and wherein at least one of the layers containing NiFe has a thickness that is greater than four hundred angstroms.
4. The disk of claim 1 , further comprising a nonmagnetic layer disposed between the underlayer and the media layer.
5. The disk of claim 1 , wherein the underlayer has a saturation magnetization of at least 2.3 tesla.
6. The disk of claim 1 , wherein the underlayer has a coercivity of not more than twelve oersted.