Shielded magnetic tunnel junction magnetoresistive read head

• US 5,898,548 A
• Filed: 10/24/1997
• Issued: 04/27/1999
• Est. Priority Date: 10/24/1997
• Status: Expired due to Term

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Parkin, Stuart Stephen Papworth, Tsang, Ching Hwa, Fontana, Robert Edward Jr., Dill, Frederick Hayes
• Primary Examiner(s): Wolff, John H.
• Application Number:
  US08/957,787
• Time in Patent Office: 550 Days
• Field of Search: 360/113, 360/126, 365/173
• US Class Current: 360/324.2
• CPC Class Codes: G11B 5/33 Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing onlySingle head using magnetic domains for scanning G11B5/4946; multiple head for scanning G11B5/4907 and subgroups ; general details therefor G11B5/133 - G11B5/255
• CPC Class Codes: G11B 5/332 using thin films G11B5/372, G11B5/3903 take precedence
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/3912 Arrangements in which the active read-out elements are transducing in association with active magnetic shields, e.g. magnetically coupled shields G11B5/3916 takes precedence

Abstract

A magnetic tunnel junction (MTJ) magnetoresistive read head for a magnetic recording system has the MTJ device located between two spaced-apart magnetic shields. The magnetic shields, which allow the head to detect individual magnetic transitions from the magnetic recording medium without interference from neighboring transitions, also function as electrical leads for connection of the head to sense circuitry. Electrically conductive spacer layers are located at the top and bottom of the MTJ device and connect the MTJ device to the shields. The thickness of the spacer layers is selected to optimize the spacing between the shields, which is a parameter that controls the linear resolution of the data that can be read from the magnetic recording medium. To reduce the likelihood of electrical shorting between the shields if the shield-to-shield spacing is too small, each of the shields can have a pedestal region with the MTJ device located between the two pedestals, so that the shield-to-shield spacing outside the pedestal regions is greater than in the pedestal regions.

Claims

1. A magnetic tunnel junction magnetoresistive read head for sensing data magnetically recorded on a medium when connected to sense circuitry, the head comprising:

a first magnetic shield formed of electrically conducting and magnetically permeable material;

a first electrically conductive spacer layer located on the first shield;

a magnetic tunnel junction located on the first spacer layer and comprising;

a fixed ferromagnetic layer having its magnetization direction fixed along a preferred direction so as to be substantially prevented from rotation in the presence of an applied magnetic field from the medium;

a sensing ferromagnetic layer having its magnetization direction oriented generally perpendicular to the magnetization direction of the fixed ferromagnetic layer in the absence of an applied magnetic field and being free to rotate in the presence of an applied magnetic field from the medium;

an insulating tunnel barrier layer located between and in contact with the fixed and sensing ferromagnetic layers for permitting tunneling current in a direction generally perpendicular to the fixed and sensing ferromagnetic layers;

a second electrically conductive spacer layer, wherein the magnetic tunnel junction is located between and in contact with the first and second spacer layers; and

a second magnetic shield formed of electrically conducting and magnetically permeable material and located on the second spacer layer;

whereby an electrically conductive path is provided from the first shield to the first spacer layer and through the magnetic tunnel junction to the second spacer layer and the second shield.

2. The head according to claim 1 further comprising a capping layer for providing corrosion protection for the magnetic tunnel junction, the capping layer being located between the magnetic tunnel junction and the second spacer layer.

3. The head according to claim 1 wherein the second spacer layer is a capping layer for providing corrosion protection for the magnetic tunnel junction.

4. The head according to claim 1 further comprising an antiferromagnetic layer in contact with the fixed ferromagnetic layer for fixing the magnetization direction of the fixed ferromagnetic layer by interfacial exchange coupling.

5. The head according to claim 4 wherein the first spacer layer is formed directly on the first shield, wherein the antiferromagnetic layer is located between the first spacer layer and the fixed ferromagnetic layer, and wherein the fixed ferromagnetic layer is formed directly on and in contact with the antiferromagnetic layer.

6. The head according to claim 5 further comprising a template layer located on the first spacer layer for enhancing the formation of the antiferromagnetic layer, and wherein the antiferromagnetic layer is formed directly on and in contact with the template layer.

7. The head according to claim 5 wherein the first spacer layer is a template layer for enhancing the formation of the antiferromagnetic layer, and wherein the antiferromagnetic layer is formed directly on and in contact with the template layer.

8. The head according to claim 1 further comprising:

a biasing ferromagnetic layer for longitudinally biasing the magnetization direction of the sensing ferromagnetic layer in a direction generally perpendicular to the magnetization direction of the fixed ferromagnetic layer in the absence of an applied magnetic field; and

an electrically insulating layer located between the biasing and sensing ferromagnetic layers for electrically isolating the biasing layer from the sensing layer; and

wherein the spacer layers are electrically isolated from the biasing layer by the insulating layer, whereby when a sense current is passed between the first and second shields it passes generally perpendicularly through the magnetic tunnel junction without passing into the biasing layer.

9. The head according to claim 1 wherein the read head is part of an integrated read/write head.

10. The head according to claim 1 further comprising sense circuitry connected to the first and second shields.

11. The head according to claim 1 wherein each of the first and second shields includes a pedestal region, and wherein the first spacer layer is formed on the pedestal region of the first shield and the second spacer layer is formed on the pedestal region of the second shield, whereby the spacing between the first and second shields is greater outside the pedestal regions than at the pedestal regions.

12. The head according to claim 11 wherein the area of each of the pedestal regions is substantially the same as the area of each of the first and second spacer layers.

13. The head according to claim 1 wherein the first and second shields are formed of a material selected from the group consisting of NiFeX alloys (where X is Ta, Rh, Pt, or Nb), CoZrNb alloys, and FeAlSi alloys.

14. The head according to claim 1 wherein the head is the type for sensing data from a magnetic recording disk and further comprising an air-bearing slider having an air-bearing surface (ABS) facing the surface of the disk when data from the disk is being read by the head and a trailing end surface generally perpendicular to the ABS, and wherein the slider trailing end surface is a substrate on which the first shield is formed.

15. A magnetoresistive read head assembly having a magnetic tunnel junction sensor for sensing magnetic transitions from a magnetic recording disk in a magnetic recording disk drive when the read head is connected to sense circuitry, the assembly comprising:

a head carrier having a sensing surface for facing the surface of the disk and a trailing end surface generally perpendicular to the sensing surface;

a first magnetic shield on the trailing end surface of the head carrier, the first shield being electrically conducting for providing an electrical lead for connection to the sense circuitry and magnetically permeable for shielding the sensor from transitions neighboring the transition being sensed;

a first electrically conductive spacer layer on the first shield;

a magnetic tunnel junction sensor on the first spacer layer comprising;

a fixed ferromagnetic layer on the first spacer layer and having its magnetization direction fixed along a preferred direction so as to be substantially prevented from rotation in the presence of an applied magnetic field from the disk;

an insulating tunnel barrier layer located on and in contact with the fixed ferromagnetic layer;

a sensing ferromagnetic layer on and in contact with the tunnel barrier layer and having its magnetization direction oriented generally perpendicular to the magnetization direction of the fixed ferromagnetic layer in the absence of an applied magnetic field and being free to rotate in the presence of an applied magnetic field from the disk;

a second electrically conductive spacer layer on the sensing ferromagnetic layer; and

a second magnetic shield located on the second spacer layer, the second shield being electrically conducting for providing an electrical lead for connection to the sense circuitry and magnetically permeable for shielding the sensor from transitions neighboring the transition being sensed;

whereby an electrically conductive path is provided from the first shield to the first spacer layer and through the magnetic tunnel junction sensor to the second spacer layer and the second shield, the path including a path for tunneling current generally perpendicularly through the tunnel barrier layer.

16. The head assembly according to claim 15 further comprising a capping layer for providing corrosion protection for the magnetic tunnel junction, the capping layer being located between the sensing ferromagnetic layer and the second spacer layer.

17. The head assembly according to claim 15 wherein the second spacer layer is a capping layer for providing corrosion protection for the magnetic tunnel junction.

18. The head assembly according to claim 15 further comprising an antiferromagnetic layer in contact with the fixed ferromagnetic layer for fixing the magnetization direction of the fixed ferromagnetic layer by interfacial exchange coupling, the antiferromagnetic layer being located between the first spacer layer and the fixed ferromagnetic layer.

19. The head assembly according to claim 18 further comprising a template layer located on the first spacer layer for enhancing the formation of the antiferromagnetic layer, and wherein the antiferromagnetic layer is located directly on and in contact with the template layer.

20. The head assembly according to claim 18 wherein the first spacer layer is a template layer for enhancing the formation of the antiferromagnetic layer, and wherein the antiferromagnetic layer is formed directly on and in contact with the template layer.

21. The head assembly according to claim 15 further comprising:

a biasing ferromagnetic layer for longitudinally biasing the magnetization direction of the sensing ferromagnetic layer in a direction generally perpendicular to the magnetization direction of the fixed ferromagnetic layer in the absence of an applied magnetic field; and

an electrically insulating layer located between the biasing and sensing ferromagnetic layers for electrically isolating the biasing layer from the sensing layer; and

wherein the spacer layers are electrically isolated from the biasing layer by the insulating layer, whereby when a sense current is passed between the first and second shields it passes generally perpendicularly through the magnetic tunnel junction without passing into the biasing layer.

22. The head assembly according to claim 15 further comprising sense circuitry connected to the first and second shields.

23. The head assembly according to claim 15 wherein each of the first and second shields includes a pedestal region, and wherein the first spacer layer is formed on the pedestal region of the first shield and the second spacer layer is formed on the pedestal region of the second shield, whereby the spacing between the first and second shields is greater outside the pedestal regions than at the pedestal regions.

24. The head assembly according to claim 23 wherein the area of each of the pedestal regions is substantially the same as the area of each of the first and second spacer layers.

25. The head assembly according to claim 15 wherein the first and second shields are formed of a material selected from the group consisting of NiFeX alloys (where X is Ta, Rh, Pt, or Nb), CoZrNb alloys, and FeAlSi alloys.

26. The head assembly according to claim 15 wherein the head carrier is an air-bearing slider and wherein the sensing surface is the air-bearing surface of the slider.