TMR device with novel free layer structure
First Claim
1. A magnetoresistive element in a magnetic device, comprising:
- (a) a synthetic anti-parallel (SyAP) pinned layer;
(b) a free layer comprised of (CoFe/CoFeB)n, (CoFeM/CoFeB)n, (CoFe/CoFeBM)n, (CoFeM/CoFeBM)n, (CoFeLM/CoFeB)n, or (CoFeLM/CoFeBM)n wherein n≧
2, L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, and L is unequal to M, and each of said CoFeB or CoFeBM layers has a greater thickness than each of said CoFe, CoFeM, or CoFeLM layers, and;
(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFe, CoFeM, or CoFeLM layer in said free layer wherein said second surface is opposite said first surface.
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Abstract
A TMR sensor that includes a free layer having at least one B-containing (BC) layer made of CoFeB, CoFeBM, CoB, COBM, or CoBLM, and a plurality of non-B containing (NBC) layers made of CoFe, CoFeM, or CoFeLM is disclosed where L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb. One embodiment is represented by (NBC/BC)n where n≧2. A second embodiment is represented by (NBC/BC)n/NBC where n≧1. In every embodiment, a NBC layer contacts the tunnel barrier and NBC layers each with a thickness from 2 to 8 Angstroms are formed in alternating fashion with one or more BC layers each 10 to 80 Angstroms thick. Total free layer thickness is<100 Angstroms. The free layer configuration described herein enables a significant noise reduction (SNR enhancement) while realizing a high TMR ratio, low magnetostriction, low RA, and low Hc values.
66 Citations
20 Claims
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1. A magnetoresistive element in a magnetic device, comprising:
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(a) a synthetic anti-parallel (SyAP) pinned layer; (b) a free layer comprised of (CoFe/CoFeB)n, (CoFeM/CoFeB)n, (CoFe/CoFeBM)n, (CoFeM/CoFeBM)n, (CoFeLM/CoFeB)n, or (CoFeLM/CoFeBM)n wherein n≧
2, L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, and L is unequal to M, and each of said CoFeB or CoFeBM layers has a greater thickness than each of said CoFe, CoFeM, or CoFeLM layers, and;(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFe, CoFeM, or CoFeLM layer in said free layer wherein said second surface is opposite said first surface. - View Dependent Claims (2, 3, 4)
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5. A magnetoresistive element in a magnetic device, comprising:
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(a) a SyAP pinned layer; (b) a free layer comprised of (CoFe/CoFeB)n/CoFe, (CoFeM/CoFeB)n/CoFeM, (CoFe/CoFeBM)n/CoFe, (CoFeM/CoFeBM)n/CoFeM, (CoFeLM/CoFeB)n/CoFeLM, or (CoFeLM/CoFeBM)n/CoFeLM wherein n≧
1, L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, and L is unequal to M, and each of said CoFeB or CoFeBM layers has a greater thickness than each of said CoFe, CoFeM, or CoFeLM layers, and;(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFe, CoFeM, or CoFeLM layer in said free layer wherein said second surface is opposite said first surface. - View Dependent Claims (6, 7, 8)
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9. A magnetoresistive element in a magnetic device, comprising:
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(a) a SyAP pinned layer; (b) a free layer comprised of (CoFe/CoB)n, (CoFeM/CoB)n, (CoFeLM/CoB)n, (CoFe/CoBM)n, (CoFeM/CoBM)n, (CoFeLM/CoBM)n, (CoFe/CoBLM)n, (CoFeM/CoBLM)n, or (CoFeLM/CoBLM)n wherein n≧
2, L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, and L is unequal to M, and each of said CoB, CoBM, or CoBLM layers has a greater thickness than each of said CoFe, CoFeM, or CoFeLM layers, and;(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFe, CoFeM, or CoFeLM layer in said free layer wherein said second surface is opposite said first surface. - View Dependent Claims (10, 11, 12)
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13. A magnetoresistive element in a magnetic device, comprising:
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(a) a SyAP pinned layer; (b) a free layer comprised of (CoFe/CoB)n/CoFe, (CoFeM/CoB)n/CoFeM, (CoFeLM/CoB)nCoBLM, (CoFe/CoBM)n/CoFe, (CoFeM/CoBM)n/CoFeM, (CoFeLM/CoBM)n/CoFeLM, (CoFe/CoBLM)n/CoFe, (CoFeM/CoBLM)n/CoFeM, or (CoFeLM/CoBLM)n/CoFeLM wherein n≧
1, L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, and L is unequal to M, and each of said CoB, CoBM, or CoBLM layers has a greater thickness than each of said CoFe, CoFeM, or CoFeLM layers, and;(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFe, CoFeM, or CoFeLM layer in said free layer wherein said second surface is opposite said first surface. - View Dependent Claims (14, 15, 16)
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17. A method of forming a sensor element in a magnetic device, comprising:
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(a) sequentially forming a stack of layers comprised of a seed layer, anti-ferromagnetic (AFM) layer, and a SyAP pinned layer having an AP2/coupling/AP1 configuration on a substrate wherein the AP2 layer contacts said AFM layer; (b) forming a tunnel barrier having a first surface that contacts said AP1 layer and a second surface opposite the first surface; (c) forming a composite free layer on the tunnel barrier, said composite free layer is comprised of; (1) at least one CoFeB, CoFeBM, CoB, CoBM, or CoBLM layer having a first thickness and where L and M are one of Ni, Ta, Ti, W, Zr, Hf, Tb, or Nb, L is unequal to M, and said at least one CoFeB, CoFeBM, CoB, CoBM, or CoBLM layer is formed in an alternating configuration with the plurality of CoFe, CoFeM, or CoFeLM layers; and (2) a plurality of CoFe, CoFeM, or CoFeLM layers each having a second thickness less than said first thickness, and one of said CoFe, CoFeM, or CoFeLM layers contacts said second surface of the tunnel barrier; and (d) forming a capping layer on the composite free layer. - View Dependent Claims (18, 19, 20)
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Specification