Underlayer for high amplitude spin valve sensors
View Patent ↗A spin valve sensor system and a method for fabricating the same are provided. Such spin valve sensor includes a pinned layer having a pinned layer magnetization. Also included is a free layer disposed adjacent the pinned layer. The free layer has a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field. A pinning layer is disposed adjacent the pinned layer for fixing the pinned layer magnetization. Further included is an underlayer disposed adjacent the pinning layer. Such underlayer comprises NiFeX. Disposed adjacent the underlayer and the pinning layer is an upper layer. The upper layer comprises a material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor.
1. A spin valve (SV) sensor, comprising:
a pinned layer having a pinned layer magnetization;
a free layer disposed towards the pinned layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field;
a spacer layer disposed between the free layer and the pinned layer;
a pinning layer disposed towards the pinned layer for fixing the pinned layer magnetization;
an underlayer disposed towards the pinning layer, the underlayer comprising NiFeX; and
an upper layer disposed adjacent the underlayer and the pinning layer, the upper layer comprising at least one material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor;
wherein the sensor provides an increase of ΔR/R of at least 5% when compared to an otherwise identical sensor not having the upper layer;
wherein the upper layer is doped with a material other than NiFe or CoFe for decreasing an electrical conductivity of the upper layer.
2. The spin valve sensor as recited in claim 1 , wherein the upper layer has a thickness of at least 4 A.
3. The spin valve sensor as recited in claim 1 , wherein the upper layer has a thickness of less than 5 A.
4. The spin valve sensor as recited in claim 1 , wherein the underlayer comprises NiFeCr.
5. The spin valve sensor as recited in claim 1 , wherein the SV sensor is a component of a disk drive system.
6. The spin valve sensor as recited in claim 1 , wherein the underlayer includes 40+/−5 Atomic % Cr.
7. The spin valve sensor as recited in claim 1 , wherein the pinned layer comprises a Ru layer, a first CoFe layer disposed adjacent a first side of the Ru layer and a second CoFe layer disposed adjacent a second side of the Ru layer.
8. The spin valve sensor as recited in claim 1 , wherein the underlayer comprises NiFeX where X is not Cr.
9. The spin valve sensor as recited in claim 1 , wherein the upper layer is non-magnetic.
10. A spin valve (SV) sensor, comprising:
a pinned layer having a pinned layer magnetization;
a free layer disposed towards the pinned layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field;
a spacer layer disposed between the free layer and the pinned layer;
a pinning layer disposed towards the pinned layer for fixing the pinned layer magnetization;
an underlayer disposed towards the pinning layer, the underlayer comprising NiFeX; and
an upper layer disposed adjacent the underlayer and the pinning layer, the upper layer comprising at least one material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor;
wherein the sensor provides an increase of ΔR/R of at least 5% when compared to an otherwise identical sensor not having the upper layer;
wherein the upper layer includes both NiFe and CoFe.
11. A method of fabricating a spin valve (SV) sensor comprising:
depositing an underlayer comprising NiFeX, where X is not Cr;
depositing an upper layer adjacent the underlayer, the upper layer comprising at least one material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor;
depositing a pinning layer towards the upper layer;
depositing a pinned layer towards the pinning layer; the pinned layer having a pinned layer magnetization;
depositing a spacer layer towards the pinned layer; and
depositing a free layer towards the spacer layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field;
wherein the upper layer is doped for at least one of reducing an electrical conductivity of the upper layer and reducing magnetic properties of the upper layer.
12. The method as recited in claim 11 , wherein the upper layer has a thickness of at least 4 A.
13. The method as recited in claim 12 , wherein the upper layer has a thickness of no more than 20 A.
14. A method of fabricating a spin valve (SV) sensor comprising:
depositing an underlayer comprising NiFeX, where X is not Cr;
depositing an upper layer adjacent the underlayer, the upper layer comprising at least one material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor;
depositing a pinning layer towards the upper layer;
depositing a pinned layer towards the pinning layer, the pinned layer having a pinned layer magnetization;
depositing a spacer layer towards the pinned layer; and
depositing a free layer towards the spacer layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field;
wherein the upper layer includes both NiFe and CoFe.
15. A spin valve (SV) sensor comprising:
a pinned layer having a pinned layer magnetization;
a free layer disposed towards the pinned layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field;
a pinning layer disposed towards the pinned layer for fixing the pinned layer magnetization;
an underlayer disposed towards the pinning layer, the underlayer comprising NiFeCr; and
an upper layer disposed adjacent the underlayer and the pinning layer, the upper layer comprising a material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor;
wherein the upper layer is doped with a material other than NiFe or CoFe for reducing at least one of an electrical conductivity of the upper layer and magnetic properties of the upper layer.
16. A spin valve (SV) sensor comprising:
a single pinned layer having a pinned layer magnetization, the pinned layer comprising a Ru layer with a first CoFe layer disposed adjacent a first side of the Ru layer and a second CoFe layer disposed adjacent a second side of the Ru layer;
a free layer disposed towards the pinned layer, the free layer having a free layer magnetization perpendicular to the pinned layer magnetization in the absence of an external field, the free layer comprising a NiFe layer with a third CoFe layer disposed adjacent thereto;
a spacer layer disposed between the free layer and the pinned layer;
a pinning layer disposed towards the pinned layer for fixing the pinned layer magnetization, the pinning layer comprising PtMn;
an underlayer disposed towards the pinning layer, the underlayer comprising NiFeCr, and
an upper layer disposed towards the underlayer and the pinning layer, the upper layer comprising a material selected from the group consisting of NiFe and CoFe for increasing a GMR ratio associated with the SV sensor
wherein the upper layer has a thickness less than 20 A;
wherein the upper layer is doped with a material other than NiFe or CoFe for reducing at least one of an electrical conductivity of the upper layer and magnetic properties of the upper layer;
wherein the sensor provides an increase of ΔR/R of at least 5% when compared to an otherwise identical sensor not having the upper layer.