Effective rear hard bias for dual free layer read heads
The present disclosure generally related to read heads having dual free layer (DFL) sensors. The read head has a sensor disposed between two shields. The sensor is a DFL sensor and has a surface at the media facing surface (MFS). Behind the DFL sensor, and 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 RHB is disposed on the insulating material. The RHB includes a RHB seed layer as well as a RHB bulk layer. The RHB seed layer has a thickness of between 26 Angstroms and 35 Angstroms. The RHB seed layer ensures the read head has a strong RHB magnetic field that can be uniformly applied.
1. A sensing element, comprising:
a sensor disposed between a first shield and a second shield; and
a rear hard bias (RHB) structure disposed between the first shield and the second shield, and behind the sensor, wherein the RHB structure comprises:
a RHB seed layer comprising a multilayer structure, wherein the RHB seed layer has a thickness that is greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms; and
a RHB bulk layer.
2. The sensing element of claim 1 , wherein the RHB seed layer has a first portion disposed between the RHB bulk layer and the first shield, and a second portion disposed between the RHB bulk layer and the sensor, wherein the first portion has a first thickness, wherein the second portion has a second thickness different than the first thickness.
3. The sensing element of claim 2 , wherein the first thickness is greater than the second thickness.
4. The sensing element of claim 3 , wherein the first thickness is greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms.
5. The sensing element of claim 1 , wherein the multilayer structure has a collective thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms.
6. The sensing element of claim 1 , wherein the RHB seed layer comprises a nonmagnetic electrically conductive material.
7. A magnetic recording device comprising the sensing element of claim 1 .
8. A sensing element, comprising:
a dual free layer (DFL) sensor;
a read hard bias (RHB) structure, wherein the RHB structure comprises a RHB seed layer having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms, wherein the RHB seed layer comprises a first layer of tantalum having a first thickness and a second layer of tungsten having a second thickness; and
an insulating material disposed between the DFL sensor and the RHB seed layer.
9. The sensing element of claim 8 , wherein the RHB structure comprises CoPt.
10. A magnetic recording device comprising the sensing element of claim 8 .
11. A sensing element, comprising:
a dual free layer (DFL) sensor;
a read hard bias (RHB) structure, wherein the RHB structure comprises a RHB seed layer having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms, and wherein the RHB seed layer comprises a first layer of tantalum having a first thickness and a second layer of tungsten having a second thickness; and
an insulating material disposed between the DFL sensor and the RHB seed layer, wherein the first layer is disposed between the insulating material and the second layer.
12. The sensing element of claim 11 , wherein the first thickness is between about 10 Angstroms and about 19 Angstroms.
13. The sensing element of claim 11 , wherein the second thickness is between about 16 Angstroms and about 25 Angstroms.
14. A sensing element, comprising:
a first sensor disposed between a first shield and a middle shield;
a second sensor disposed between the middle shield and a second shield;
a first rear hard bias (RHB) structure disposed between the first shield and the middle shield; and
a second RHB structure disposed between the middle shield and the second shield, wherein at least one of the first RHB structure and the second RHB structure includes a first RHB seed layer comprising tantalum having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms.
15. The sensing element of claim 14 , wherein the first RHB structure includes the first RHB seed layer.
16. The sensing element of claim 15 , wherein the second RHB structure includes a second RHB seed layer having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms.
17. A magnetic recording device comprising the sensing element of claim 14 .
18. A sensing element, comprising:
a first sensor disposed between a first shield and a middle shield;
a second sensor disposed between the middle shield and a second shield;
a first rear hard bias (RHB) structure disposed between the first shield and the middle shield; and
a second RHB structure disposed between the middle shield and the second shield, wherein at least one of the first RHB structure and the second RHB structure includes a first RHB seed layer having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms,
wherein the first RHB structure includes the first RHB seed layer, wherein the second RHB structure includes a second RHB seed layer having a thickness that is both greater than or equal to 26 Angstroms and less than or equal to 35 Angstroms, wherein the first RHB seed layer comprises tantalum, and wherein the second RHB seed layer comprises tungsten.