CPP GMR and magnetostriction improvement by laminating Co90Fe10free layer with thin Fe50Co50layers
First Claim
1. A current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) magnetic field sensor of the synthetic spin valve type comprising:
- a substrate;
a seed layer formed on the substrate;
an antiferromagnetic pinning layer formed on the seed layer;
a synthetic antiferromagnetic pinned layer formed on the pinning layer, said pinned layer further comprising ferromagnetic layer AP2, formed on said pinning layer, a non-magnetic coupling layer formed on AP2 and ferromagnetic layer AP1 formed on said coupling layer;
a spacer layer formed on said AP1 layer;
a laminated free layer formed on said spacer layer, the free layer including a plurality of layers of a second ferromagnetic material, each said layer being formed to a thickness between approximately 2.5 and 15 angstroms and each said layer being separated from an adjacent said layer by a lamina of a first ferromagnetic material formed to a thickness less than approximately 3 angstroms or by a Cu spacer layer formed to a thickness between approximately 1 and 4 angstroms; and
wherein each said lamina of said first ferromagnetic material has a positive coefficient of magnetostriction and each said layer of said second ferromagnetic material has a negative coefficient of magnetostriction, whereby the coefficient of magnetostriction of said free layer can be made positive or negative, wherein said laminated free layer includes at least one lamina of said first ferromagnetic material; and
a capping layer formed on said free layer.
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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 CoxFe1−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.
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Citations
13 Claims
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1. A current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) magnetic field sensor of the synthetic spin valve type comprising:
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a substrate; a seed layer formed on the substrate; an antiferromagnetic pinning layer formed on the seed layer; a synthetic antiferromagnetic pinned layer formed on the pinning layer, said pinned layer further comprising ferromagnetic layer AP2, formed on said pinning layer, a non-magnetic coupling layer formed on AP2 and ferromagnetic layer AP1 formed on said coupling layer; a spacer layer formed on said AP1 layer; a laminated free layer formed on said spacer layer, the free layer including a plurality of layers of a second ferromagnetic material, each said layer being formed to a thickness between approximately 2.5 and 15 angstroms and each said layer being separated from an adjacent said layer by a lamina of a first ferromagnetic material formed to a thickness less than approximately 3 angstroms or by a Cu spacer layer formed to a thickness between approximately 1 and 4 angstroms; and
wherein each said lamina of said first ferromagnetic material has a positive coefficient of magnetostriction and each said layer of said second ferromagnetic material has a negative coefficient of magnetostriction, whereby the coefficient of magnetostriction of said free layer can be made positive or negative, wherein said laminated free layer includes at least one lamina of said first ferromagnetic material; anda capping layer formed on said free layer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of forming a current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) magnetic field sensor of the synthetic spin valve type having a coefficient of magnetostriction that can be varied from positive to negative by changing a laminated configuration of its free layer comprising:
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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 spacer layer on said AP1 layer; forming a laminated free layer on the spacer layer, said laminated free layer including a plurality of layers of a second ferromagnetic material, each said layer being formed to a thickness between approximately 2.5 and 15 angstroms and each said layer being separated from an adjacent said layer by a lamina of a first ferromagnetic material formed to a thickness less than approximately 3 angstroms or by a Cu spacer layer formed to a thickness between approximately 1 and 4 angstroms; and
wherein each lamina of said first ferromagnetic material has a positive coefficient of magnetostriction and each layer of said second ferromagnetic material has a negative coefficient of magnetostriction, whereby the number and arrangement of laminas of said first ferromagnetic material and the number and arrangement 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, wherein said laminated free layer includes at least one lamina of said first ferromagnetic material;
thenforming a capping layer on said free layer. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification