UNDERLAYER FOR REFERENCE LAYER OF POLYCRYSTALLINE CPP GMR SENSOR STACK
Embodiments disclosed herein generally relate to a magnetic head having an amorphous ferromagnetic reference layer. The ferromagnetic reference layer may have amorphous structure as a result of an amorphous ferromagnetic underlayer that the ferromagnetic reference layer is deposited thereon. The amorphous ferromagnetic reference layer enhances magnetoresistance, leading to an improved magnetic head.
1 . A magnetic head, comprising:
a sensor stack, wherein the sensor stack includes:
an antiferromagnetic layer;
a ferromagnetic pinned layer disposed on the antiferromagnetic layer;
a first nonmagnetic layer disposed on the ferromagnetic pinned layer;
a first crystalline ferromagnetic underlayer disposed on the first nonmagnetic layer;
an amorphous ferromagnetic reference layer disposed over the first crystalline ferromagnetic underlayer;
a second nonmagnetic layer disposed on the amorphous ferromagnetic reference layer;
a second crystalline ferromagnetic underlayer disposed on the second nonmagnetic layer; and
a ferromagnetic free layer disposed over the second crystalline ferromagnetic underlayer.
2 . The magnetic head of claim 1 , further comprising a first amorphous ferromagnetic underlayer disposed between the first crystalline ferromagnetic underlayer and the amorphous ferromagnetic reference layer.
3 . The magnetic head of claim 2 , wherein the first amorphous ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe.
4 . The magnetic head of claim 2 , further comprising a second amorphous ferromagnetic underlayer disposed between the second crystalline ferromagnetic underlayer and the ferromagnetic free layer.
5 . The magnetic head of claim 4 , wherein the second amorphous ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe.
6 . The magnetic head of claim 1 , wherein the ferromagnetic free layer is amorphous.
7 . The magnetic head of claim 1 , wherein the amorphous ferromagnetic reference layer is deposited on the first crystalline ferromagnetic underlayer at a temperature between about 50 K to about 100 K.