# US 9,040,178 B2 · TMR device with novel free layer structure

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- Number: US 9,040,178 B2
- Document ID: US9040178B2
- Status: Granted
- Kind: B2
- Application number: 12/284,409
- Filed: 2008-09-22
- Published: 2010-03-25
- Granted: 2015-05-26
- Earliest claimed: 2008-09-22
- Assignees: Headway Technologies, Inc.
- Applicants: Tong Zhao; Hui-Chuan Wang; Yu-Chen Zhou; Min Li; Kunliang Zhang
- Inventors: Tong Zhao; Hui-Chuan Wang; Yu-Chen Zhou; Min Li; Kunliang Zhang
- Web page: https://patentgrep.com/patent/US9040178B2

## CPC

- H10N 50/01: Manufacture or treatment
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- B82Y 25/00: Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
- G01R 33/098: {comprising tunnel junctions, e.g. tunnel magnetoresistance sensors}
- G11B 5/3909: {Arrangements using a magnetic tunnel junction}
- G11B 5/3929: {Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding}
- H10N 50/10: Magnetoresistive devices
- H10N 50/85: Materials of the active region
- G11B 2005/3996: {large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices}
- Y10T 428/1114: having tunnel junction effect
- Y10T 428/1121: Multilayer
- Y10T 428/1143: with defined structural feature
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## 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.

## Claims

### Claim 1

A magnetoresistive element in a magnetic device, comprising:
(a) a synthetic anti-parallel (SyAP) pinned layer;
(b) a free layer consisting of (CoFeTb/CoFeB)n, (CoFeTb/CoFeBTb)n,(CoFeTbL/CoFeB)n, or (CoFeTbL/CoFeBTb)n wherein n≧2, L is one of Ni, Ti, W, Zr, Hf, or Nb and has a content greater than 0 atomic %, and each of said CoFeB or CoFeBTb layers has a greater thickness than each of said CoFeTb, or CoFeTbL layers in the free layer wherein a boron containing layer alternates with a non-boron containing layer, and all layers in the free layer have at least one non-magnetic element, and;
(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFeTb, or CoFeTbL layer in said free layer wherein said second surface is opposite said first surface.

### Claim 2 (depends on 1)

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 CoFeBTb layers is between about 5 and 40 atomic %.

### Claim 3 (depends on 1)

The magnetoresistive element of claim 1 wherein each of said CoFeTb, or CoFeTbL layers has a thickness between about 2 and 8 Angstroms and each of said CoFeB or CoFeBTb layers has a thickness from about 10 to 80 Angstroms.

### Claim 4 (depends on 1)

The magnetoresistive element of claim 1 wherein the tunnel barrier layer is comprised of MgO, MgZnO, ZnO, Al2O3, TiOx, AITiO, HfOx, ZrOx, or a combination of two or more of the aforementioned materials.

### Claim 5 (depends on 1)

The magnetoresistive element of claim 1 wherein Tb in the CoFeTb or CoFeBTb layer is less than about 10 atomic %.

### Claim 6 (depends on 1)

The magnetoresistive element of claim 1 wherein a total of L and Tb in the CoFeTbL layer is less than about 10 atomic %.

### Claim 7 (depends on 1)

The magnetoresistive element of claim 1 wherein the free layer has a thickness less than about 100 Angstroms.

### Claim 8

A magnetoresistive element in a magnetic device, comprising:
(a) a synthetic anti-parallel (SyAP) pinned layer;
(b) a free layer consisting of (CoFeTb/[Co(100-X)FeX]100-YBY)n, (CoFeTb/CoFeBTb)n, (CoFeTbL/[Co(100-X)FeX]100-YBY)n, or (CoFeTbL/CoFeBTb)n wherein n≧2, x=0 or 100 atomic %, y is from 10 to 40 atomic %, L is one of Ni, Ta, Ti, W, Zr, Hf, or Nb and has a content greater than 0 atomic %, and each of said [Co(100-X)FeX]100-YBY or CoFeBTb layers has a greater thickness than each of said CoFeTb, or CoFeTbL layers in the free layer wherein a boron containing layer alternates with a non-boron containing layer, and all layers in the free layer have at least one non-magnetic element, and;
(c) a tunnel barrier layer having a first surface that contacts the SyAP pinned layer and a second surface that contacts a CoFeTb, or CoFeTbL layer in said free layer wherein said second surface is opposite said first surface.