Transverse bias strength enhancement in dual free layer tunnel magnetoresistive read heads
The present disclosure generally related to read heads having dual free layer (DFL) sensors. The DFL sensor and has a surface at the media facing surface (MFS). Behind the DFL sensor away from the MFS, is a rear hard bias (RHB) structure. The RHB structure is disposed between the shields as well. In between the DFL sensor and the RHB structure is insulating material. The insulating material is a multilayer structure. A first layer of the multilayer structure is composed of the same material as the tunnel magnetoresistive barrier layer, such as MgO, and is disposed adjacent the DFL sensor, yet spaced from the RHB structure. A second layer of the multilayer structure is a different insulating layer that is disposed adjacent the RHB structure, yet spaced from the DFL sensor. The multilayer structure helps improve areal density without degrading head stability and performance reliability by maintaining RHB coercivity.
1. A magnetic read head, comprising:
a first shield;
a second shield spaced from the first shield;
a sensor disposed between the first shield and the second shield, wherein the first shield, the second shield, and the sensor each has a surface at a media facing surface (MFS) of the magnetic read head;
a rear hard bias (RHB) structure disposed between the first shield and the second shield, and behind the sensor, wherein the RHB structure is spaced from the MFS; and
a multilayer insulating structure, wherein each layer of the multilayer insulating structure is disposed between the sensor and the RHB structure and sandwiched between the RHB structure and the first shield.
2. The magnetic read head of claim 1 , wherein the multilayer insulating structure comprises at least a first layer and a second layer, and wherein the first layer and the second layer comprise different materials.
3. The magnetic read head of claim 1 , wherein the multilayer insulating structure comprises at least one layer that is chemically compatible to a tunnel magnetoresistive (TMR) barrier and capable of functioning as a TMR insulation layer, and wherein the at least one layer that is capable of functioning as a TMR insulation layer is spaced from the RHB structure.
4. The magnetic read head of claim 3 , wherein the at least one layer that is chemically compatible to the TMR barrier and capable of functioning as a TMR insulation layer has a compressive stress that is greater than a compressive stress of all other layers of the multilayer insulating structure.
5. The magnetic read head of claim 1 , wherein the multilayer insulating structure is deposited by ion beam sputter deposition.
6. A magnetic recording device comprising the magnetic read head of claim 1 .
7. A sensing element, comprising:
a dual free layer (DFL) sensor;
a read hard bias (RHB) structure; and
a multilayer insulating structure coupled between the DFL sensor and a first surface of the RHB structure, wherein the multilayer insulating structure comprises at least one layer that is chemically compatible to a tunnel magnetoresistive (TMR) barrier and capable of functioning as a TMR insulation layer, and wherein each layer of the multilayer insulating structure extends along the first surface of the RHB structure and a second surface of the RHB structure disposed substantially perpendicular to the first surface.
8. The sensing element of claim 7 , wherein the multilayer insulating structure comprises a first layer and a second layer, wherein the first layer is disposed between the sensor and the second layer, and wherein the first layer comprises MgO.
9. The sensing element of claim 8 , wherein the second layer comprises Al 2 O 3 .
10. The sensing element of claim 9 , wherein the RHB structure comprises CoPt.
11. The sensing element of claim 7 , wherein the at least one layer that is chemically compatible to the TMR barrier and capable of functioning as the TMR insulation layer is spaced from the RHB structure.
12. The sensing element of claim 7 , wherein the at least one layer that is chemically compatible to the TMR barrier and capable of functioning as the TMR insulation layer is in contact with the DFL sensor.
13. The sensing element of claim 7 , wherein each layer of the multilayer insulating structure has a substantially constant thickness.
14. A magnetic recording device comprising the sensing element of claim 7 .
15. A magnetic read head, comprising:
a first shield;
a middle shield;
a second shield;
a first sensor disposed between the first shield and the middle shield;
a second sensor disposed between the middle shield and the second shield;
at least one first rear hard bias (RHB) structure disposed between the first shield and the second shield; and
a first multilayer insulating structure comprising at least one layer that is chemically compatible to a tunnel magnetoresistive (TMR) barrier and capable of functioning as a TMR insulation layer, wherein each layer of the first multilayer insulating structure is disposed between the at least one first RHB structure and the first sensor and sandwiched between the at least one first RHB structure and the first shield.
16. The magnetic read head of claim 15 , further comprising:
at least one second RHB structure disposed between the middle shield and the second shield; and
a second multilayer insulating structure disposed between the at least one second RHB structure and the second sensor, wherein the second multilayer insulating structure comprises at least one layer that is chemically compatible to the TMR barrier and capable of functioning as the TMR insulation layer.
17. The magnetic read head of claim 16 , wherein each layer of the second multilayer insulating structure is disposed between the at least one second RHB structure and the second sensor and sandwiched between the at least one second RHB structure and the middle shield.
18. The magnetic read head of claim 15 , wherein the first multilayer insulating structure is disposed between the first shield and the at least one first RHB structure.
19. The magnetic read head of claim 15 , wherein the first sensor and the second sensor are dual free layer (DFL) sensors.
20. A magnetic recording device comprising the magnetic read head of claim 15 .