Current-perpendicular-to-plane (CPP) read sensor with multiple reference layers
View Patent ↗A current-to-perpendicular-to-plane (CPP) read sensor with multiple reference layers and associated fabrication methods are disclosed. According to one embodiment of the invention, the multiple reference layers of a CPP tunneling magnetoresistance (TMR) read sensor includes a first reference layer formed by a ferromagnetic polycrystalline Co—Fe film, a second reference layer formed by a ferromagnetic substitute-type amorphous Co—Fe—X film where X is Hf, Zr or Y, and a third reference layer formed by a ferromagnetic interstitial-type amorphous Co—Fe—B film. The first reference layer facilitates the CPP TMR read sensor to exhibit high exchange and antiparallel-coupling fields. The second reference layer provides a thermally stable flat surface, thus facilitating the CPP TMR read sensor to exhibit a low ferromagnetic-coupling field. The multiple reference layers may induce spin-dependent scattering, thus facilitating the CPP TMR sensor to exhibit a high TMR coefficient.
1. A flux-closure structure for a current-perpendicular-to-plane (CPP) read sensor, the flux-closure structure comprising:
a keeper layer;
an antiparallel coupling layer on the keeper layer; and
multiple reference layers on the antiparallel coupling layer, the multiple reference layers comprising:
a first reference layer formed by a ferromagnetic polycrystalline film on the antiparallel coupling layer;
a second reference layer formed by a ferromagnetic substitute-type amorphous film on the first reference layer; and
a third reference layer formed by a ferromagnetic interstitial-type amorphous film on the second reference layer.
2. The flux-closure structure of claim 1 wherein the first reference layer is formed by a Co—Fe film including Co with a content ranging from 50 to 90 at % and Fe with a content ranging from 10 to 50 at %, and having a thickness ranging from 0.2 to 1 nanometers.
3. The flux-closure structure of claim 1 wherein the second reference layer is formed by a Co—Fe—X film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and X with a content ranging from 6 to 30 at %, where X is Hf, Zr or Y, and having a thickness ranging from 0.6 to 2 nanometers.
4. The flux-closure structure of claim 1 wherein the third reference layer is formed by a Co—Fe—B film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and B with a content ranging from 6 to 30 at %, and having a thickness ranging from 1 to 2 nanometers.
5. A current-perpendicular-to-plane (CPP) read sensor, comprising:
nonmagnetic seed layers;
an antiferromagnetic pinning layer on the seed layers;
a flux-closure structure on the antiferromagnetic pinning layer, wherein the flux-closure structure includes:
a keeper layer;
an antiparallel coupling layer on the keeper layer;
multiple reference layers on the antiparallel coupling layer, the multiple reference layers comprising:
a first reference layer formed by a ferromagnetic polycrystalline film on the antiparallel coupling layer;
a second reference layer formed by a ferromagnetic substitute-type amorphous film on the first reference layer; and
a third reference layer formed by a ferromagnetic interstitial-type amorphous film on the second reference layer;
a nonmagnetic spacer or barrier layer on the flux-closure structure;
ferromagnetic sense layers on the nonmagnetic spacer or barrier layer; and
a nonmagnetic cap layer on the sense layers.
6. The CPP read sensor of claim 5 wherein the first reference layer is formed by a Co—Fe film including Co with a content ranging from 50 to 90 at % and Fe with a content ranging from 10 to 50 at %, and having a thickness ranging from 0.2 to 1 nanometers.
7. The CPP read sensor of claim 5 wherein the second reference layer is formed by a Co—Fe—X film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and X with a content ranging from 6 to 30 at %, where X is Hf, Zr or Y, and having a thickness ranging from 0.6 to 2 nanometers.
8. The CPP read sensor of claim 5 wherein the third reference layer is formed by a Co—Fe—B film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and B with a content ranging from 6 to 30 at %, and having a thickness ranging from 1 to 2 nanometers.
9. The CPP read sensor of claim 5 wherein the nonmagnetic spacer layer is formed by a nonmagnetic electrically conducting Cu or oxygen-doped Cu (Cu—O) film with a thickness ranging from 1.6 to 4 nanometers for detecting resistance changes through a giant magnetoresistance effect.
10. The CPP read sensor of claim 5 wherein the nonmagnetic barrier layer is formed by a nonmagnetic electrically insulating oxygen-doped Mg (Mg—O)or Mg oxide (MgO X ) film with a thickness ranging from 0.4 to 1 nanometers.
11. A hard disk drive, comprising:
a hard disk; and
a read head that includes a current-perpendicular-to-plane (CPP) read sensor for reading data from the hard disk, the CPP read sensor comprising:
nonmagnetic seed layers;
an antiferromagnetic pinning layer on the seed layers;
a flux-closure structure on the antiferromagnetic pinning layer, wherein the flux-closure structure includes:
a keeper layer;
an antiparallel coupling layer on the keeper layer;
multiple reference layers on the antiparallel coupling layer, the multiple reference layers comprising:
a first reference layer formed by a ferromagnetic polycrystalline film on the antiparallel coupling layer;
a second reference layer formed by a ferromagnetic substitute-type amorphous film on the first reference layer; and
a third reference layer formed by a ferromagnetic interstitial-type amorphous film on the second reference layer;
a nonmagnetic spacer or barrier layer on the flux-closure structure;
ferromagnetic sense layers on the nonmagnetic spacer or barrier layer; and
a nonmagnetic cap layer on the sense layers.
12. The hard disk drive of claim 11 wherein the first reference layer is formed by a Co—Fe film including Co with a content ranging from 50 to 90 at % and Fe with a content ranging from 10 to 50 at %, and having a thickness ranging from 0.2 to 1 nanometers.
13. The hard disk drive of claim 11 wherein the second reference layer is formed by a Co—Fe—X film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and X with a content ranging from 6 to 30 at %, where X is Hf, Zr or Y, and Y, and having a thickness ranging from 0.6 to 2 nanometers.
14. The hard disk drive of claim 11 wherein the third reference layer is formed by a Co—Fe—B film including Co with a content ranging from 60 to 80 at %, Fe with a content ranging from 0 to 40 at %, and B with a content ranging from 6 to 30 at %, and having a thickness ranging from 1 to 2 nanometers.
15. A current-perpendicular-to-plane (CPP) read sensor, comprising:
a keeper layer;
an antiparallel coupling layer on the keeper layer;
a first reference layer formed by a ferromagnetic polycrystalline film on the antiparallel coupling layer; and
a second reference layer formed by a ferromagnetic amorphous film on the first reference layer.
16. The CPP read sensor of claim 15 wherein:
the first reference layer is formed by a Co—Fe film;
the second reference layer is formed by a Co—Fe—X film, where X is Zr, Hf or Y;
a third reference layer is formed by a Co—Fe—B ferromagnetic amorphous film on the second reference layer.