CPP GMR and magnetostriction improvement by laminating Co90Fe10 free layer with thin Fe50Co50 layers

• US 20050186452A1
• Filed: 02/25/2004
• Published: 08/25/2005
• Est. Priority Date: 02/25/2004
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated
• Original Assignee: Headway Technologies Incorporated
• Inventors: Liu, Yue, Zhang, Kunliang, Li, Min, Sbiaa, Rachid, Liao, Simon
• Granted Patent: US 7,141,314 B2
• Time in Patent Office: Days
• US Class Current: 428/828
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: Y10T 428/1121 Multilayer
• CPC Class Codes: Y10T 428/1143 with defined structural feature
• CPC Class Codes: Y10T 428/115 Magnetic layer composition

Abstract

A current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) sensor of the synthetic spin valve type and its method of formation are disclosed, the sensor including a novel laminated free layer having ultra-thin (less than 3 angstroms thickness) laminas of Fe₅₀ Co₅₀ (or any iron rich alloy of the form Co_xFe_1-x with x between 0.25 and 0.75) interspersed with thicker layers of Co₉₀Fe₁₀ and Cu spacer layers to produce a free layer with good coercivity, a coefficient of magnetostriction that can be varied between positive and negative values and a high GMR ratio, due to enhancement of the bulk scattering coefficient by the laminas. The configuration of the lamina and layers in periodic groupings allow the coefficient of magnetostriction to be finely adjusted and the coercivity and GMR ratio to be optimized. The sensor performance can be further improved by including layers of Cu and Fe₅₀Co₅₀ in the synthetic antiferromagnetic pinned layer.

Claims

4-1. The sensor of claim 1, 2, 3 or 4 wherein at least one layer of the second ferromagnetic material is formed on a Cu spacer layer of thickness between approximately 1 and 4 angstroms.

12. A method of forming a current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) magnetic field sensor of the synthetic spin valve type having improved GMR qualities and a coefficient of magnetostriction that can be varied from positive to negative by changing a laminated configuration of its free layer comprising:

providing a substrate;

forming a seed layer on the substrate;

forming an antiferromagnetic pinning layer on the seed layer;

forming a synthetic antiferromagnetic pinned layer on the pinning layer, said formation further comprising forming ferromagnetic layer AP2 on said pinning layer, forming a non-magnetic coupling layer on AP2 and forming ferromagnetic layer AP1 on said coupling layer;

forming a laminated free layer on the pinned layer, said laminated free layer including at least one ultra-thin lamina of a first ferromagnetic material having a positive coefficient of magnetostriction and at least one layer of a second ferromagnetic material having a negative coefficient of magnetostriction, wherein the number of laminas and the number of layers of said second ferromagnetic material determine a coefficient of magnetostriction of the free layer having a value within a range from positive to negative;

a capping layer formed on said free layer.

13. The method of claim 12, wherein said first ferromagnetic material is the iron rich ferromagnetic alloy of the form Co_xFe_1-x with x between 0.25 and 0.75 and said second ferromagnetic material is Co₉₀Fe₁₀.

14. The method of claim 13 wherein each lamina of said first ferromagnetic material is formed to a thickness that is less than approximately 3 angstroms and wherein each layer of said second ferromagnetic material is formed to a thickness between approximately 2.5 and 15 angstroms.

15. The method of claim 13 wherein said AP1 layer includes at least one layer of said first ferromagnetic material formed to a thickness between approximately 2.5 and 15 angstroms, at least one layer of said second ferromagnetic material of thickness between approximately 2.5 and 15 angstroms.

16. The method of claim 12, 13, 14 or 15 wherein at least one layer of the second ferromagnetic material is formed on a Cu spacer layer of thickness between approximately 1 and 4 angstroms.

17. The method of claim 12, 13, 14 or 15 wherein at least one layer of the second ferromagnetic material has a Cu spacer layer of thickness between approximately 1 and 4 angstroms formed thereupon.

18. The method of claim 12, 13, 14 or 15 wherein at least one lamina of the first ferromagnetic material is formed on a Cu spacer layer of thickness between approximately 1 and 4 angstroms.

19. The method of claim 12, 13, 14 or 15 wherein at least one lamina of the first ferromagnetic material has a Cu spacer layer of thickness between approximately 1 and 4 angstroms formed thereupon.

20. The method of claim 12 wherein formation of said free layer comprises:

forming a first layer of Co₉₀Fe₁₀;

forming a first lamina of Fe₅₀Co₅₀ on said first layer;

forming a second layer of Co₉₀Fe₁₀ on said first lamina;

forming a first spacer layer of Cu on said first lamina;

forming a third layer of Co₉₀Fe₁₀ on said first spacer layer;

forming a second lamina of Fe₅₀Co₅₀ on said second layer;

forming a fourth layer of Co₉₀Fe₁₀ on said second lamina;

forming a second spacer layer of Cu on said third layer;

forming a fifth layer of Co₉₀Fe₁₀ on said second spacer layer.

21. The method of claim 20 wherein the thickness said first layer is between approximately 5 and 15 angstroms, the thickness of said second, third, fourth and fifth layers is between approximately 2.5 and 7.5 angstroms, the thickness of each lamina is less than approximately 3 angstroms and the thickness of each spacer layer is between approximately 1 and 4 angstroms.

22. The method of claim 12 wherein the laminated configuration of the free layer produces a positive coefficient of magnetostriction.