TMR device with novel free layer structure

Patent metadata

Field	Value
Publication number	US-9577184-B2
Application number	US-201514712942-A
Country	US
Kind code	B2
Filing date	May 15, 2015
Priority date	Sep 22, 2008
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

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.

First claim

We claim:

1. A magnetoresistive element in a magnetic device, comprising:
(a) a SyAP pinned layer;
(b) a free layer consisting of (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 is one of Ta, Ti, W, Zr, Hf, Tb, or Nb, M is one of Ta, Ti, W, Hf, or Tb, 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.

2. The magnetoresistive element of claim 1 wherein the boron content in each of said CoFeB layers is between about 10 and 40 atomic % and the boron content in each of said CoFeBM layers is between about 5 and 40 atomic %.

3. The magnetoresistive element of claim 1 wherein each of said CoFe, CoFeM, or CoFeLM layers has a thickness between about 2 and 8 Angstroms and each of said CoFeB or CoFeBM layers has a thickness from about 10 to 80 Angstroms.

4. The magnetoresistive element of claim 1 wherein the M content in said CoFeM alloy and the L+M content in said CoFeLM alloy is less than about 10 atomic %.

5. A magnetoresistive element in a magnetic device, comprising:
(a) a SyAP pinned layer;
(b) a free layer consisting of (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.

6. The magnetoresistive element of claim 5 wherein the boron content in each of said CoB layers is between about 5 and 30 atomic %.

7. The magnetoresistive element of claim 5 wherein each of said CoFe, CoFeM, or CoFeLM layers has a thickness between about 2 and 8 Angstroms and each of said CoB, CoBM, or CoBLM layers has a thickness from about 10 to 80 Angstroms.

8. The magnetoresistive element of claim 5 wherein the tunnel barrier layer is comprised of MgO, MgZnO, ZnO, Al 2 O 3 , TiOx, AlTiO, HfOx, ZrOx, or a combination of two or more of the aforementioned materials.

9. A magnetoresistive element in a magnetic device, comprising:
(a) a SyAP pinned layer;
(b) a free layer consisting of (CoFeM/CoB) n /CoFeM, (CoFeLM/CoB) n /CoFeLM, (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 is one of Ta, Ti, W, Zr, Hf, Tb, or Nb, M is one of Ta, Ti, W, Hf, or Tb, 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.

10. The magnetoresistive element of claim 9 wherein the boron content in each of said CoB layers is between about 5 and 30 atomic %.

11. The magnetoresistive element of claim 9 wherein each of said CoFe, CoFeM, or CoFeLM layers has a thickness between about 2 and 8 Angstroms and each of said CoB, CoBM, or CoBLM layers has a thickness from about 10 to 80 Angstroms.

12. The magnetoresistive element of claim 9 wherein the M content in said CoFeM alloy and the L+M content in said CoFeLM alloy is less than about 10 atomic %.

Assignees

• Headway Tech Inc

Inventors

• Zhao Tong
• Wang Hui-Chuan
• Zhou yu-chen
• Li Min
• Zhang Kunliang

Classifications

• Y10T428/1114

  having tunnel junction effect · CPC title

• Y10T428/1121

  Multilayer · CPC title

• G11B5/3929

  Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding · CPC title

• Y10T428/1143

  with defined structural feature · CPC title

• G01R33/098

  comprising tunnel junctions, e.g. tunnel magnetoresistance sensors · CPC title