Dual free layer magnetic reader having a rear bias structure including a soft bias layer
View Patent ↗A method and system provide a magnetic read apparatus having an air-bearing surface (ABS). The read apparatus includes a read sensor, a side bias structure and a rear magnetic bias structure. The read sensor includes first and second free layers, a spacer layer and a rear surface opposite to the ABS. The spacer layer is nonmagnetic and between the first and second free layers. The side bias structure is adjacent to the side surface(s) and magnetically biases the first and second free layers to be antiferromagnetically aligned. The rear magnetic bias structure biases the free layers in a scissor mode. The read sensor is between the ABS and the rear magnetic bias structure. The rear magnetic bias structure includes a rear soft magnetic bias structure having a saturation magnetization-thickness product of at least one milli-emu/cm 2 and not more than three milli-emu/cm 2 .
1. A magnetic read apparatus having an air-bearing surface (ABS) comprising:
a read sensor including a first free layer having a first upper surface and a first lower surface, a spacer layer, and a second free layer having a second lower surface and a second upper surface, the spacer layer being nonmagnetic and residing between the upper surface of the first free layer and the lower surface of second free layer, the read sensor having a rear surface opposite to the ABS;
a side bias structure adjacent to at least one side surface of the read sensor, the side bias structure being configured to magnetically bias the first free layer and the second free layer to be antiferromagnetically aligned; and
a rear magnetic bias structure configured to bias the first free layer and the second free layer in a scissor mode, the read sensor being between the ABS and the rear magnetic bias structure, the rear magnetic bias structure including a rear soft magnetic bias structure having a saturation magnetization-thickness product of at least one milli-emu/cm 2 and not more than three milli-emu/cm 2 .
2. The magnetic read apparatus of claim 1 wherein the read sensor has a track width of not more than thirty nanometers and wherein the rear soft magnetic bias structure has a width of at least thirty nanometers.
3. The magnetic read apparatus of claim 2 wherein the track width is not more than twenty nanometers and the width of the rear soft magnetic bias structure is at least twenty nanometers.
4. The magnetic read apparatus of claim 1 wherein the rear soft magnetic bias structure is a NiFe rear soft magnetic bias structure.
5. The magnetic read apparatus of claim 1 wherein the rear magnetic bias structure further includes a rear hard magnetic bias structure, the rear soft magnetic bias magnetic structure being between the read sensor and the rear hard magnetic bias structure.
6. The magnetic read apparatus of claim 5 wherein the rear soft magnetic bias structure has a soft bias width, the read sensor has a track width, the rear hard magnetic bias structure has a hard bias width and wherein the soft bias width is at least the track width and not more than the hard bias width.
7. The magnetic read apparatus of claim 5 wherein the rear hard magnetic bias structure is separated from the rear soft magnetic bias structure by at least ten Angstroms and not more than forty Angstroms.
8. The magnetic read apparatus of claim 1 wherein the rear soft magnetic bias structure is at least ten Angstroms and not more than forty Angstroms from the read sensor.
9. The magnetic read apparatus of claim 1 further comprising:
a bottom shield; and
a top shield, the read sensor residing between the bottom shield and the top shield.
10. The magnetic read apparatus of claim 9 wherein the rear soft bias structure is coupled to the bottom shield.
11. The magnetic read apparatus of claim 9 wherein the rear soft bias structure is coupled to the top shield.
12. The magnetic read apparatus of claim 1 wherein the saturation magnetization-thickness product is not more than two milli-emu per cm 2 .
13. The magnetic read apparatus of claim 1 wherein the side bias structure further comprises a first magnetic structure, a second magnetic structure and a nonmagnetic structure between the first magnetic structure and the second magnetic structure, the first magnetic structure and the second magnetic structure being antiferromagnetically aligned.
14. The magnetic read apparatus of claim 1 wherein the rear soft bias structure has a depth in a stripe direction perpendicular to the ABS, width in a cross-track direction, and a height in a down-track direction, the depth being greater than the width and greater than the height.
15. A disk drive comprising:
at least one disk;
at least one slider including at least one magnetic transducer having an air-bearing surface (ABS), the at least one magnetic transducer including a read sensor, a side bias structure and a rear magnetic bias structure, the read sensor including a first free layer having a first upper surface and a first lower surface, a spacer layer, and a second free layer having a second lower surface and a second upper surface, the spacer layer being nonmagnetic and residing between the upper surface of the first free layer and the lower surface of second free layer, the read sensor having a rear surface opposite to the ABS, the side bias structure being adjacent to at least one side surface of the read sensor, the side bias structure being configured to magnetically bias the first free layer and the second free layer to be antiferromagnetically aligned, the rear magnetic bias structure being configured to bias the first free layer and the second free layer in a scissor mode, the read sensor being between the ABS and the rear magnetic bias structure, the rear magnetic bias structure including a rear soft magnetic bias structure having a saturation magnetization-thickness product of at least one milli-emu/cm 2 and not more than three milli-emu/cm 2 .
16. A method for providing a magnetic read apparatus having an air-bearing surface (ABS) comprising:
providing a read sensor including a first free layer having a first upper surface and a first lower surface, a spacer layer, and a second free layer having a second lower surface and a second upper surface, the spacer layer being nonmagnetic and residing between the upper surface of the first free layer and the lower surface of second free layer, the read sensor having a rear surface opposite to the ABS;
providing a side bias structure adjacent to at least one side surface of the read sensor, the side bias structure being configured to magnetically bias the first free layer and the second free layer to be antiferromagnetically aligned; and
providing a rear magnetic bias structure configured to bias the first free layer and the second free layer in a scissor mode, the read sensor being between the ABS and the rear magnetic bias structure, the rear magnetic bias structure including a rear soft magnetic bias structure having a saturation magnetization-thickness product of at least one milli-emu/cm 2 and not more than three milli-emu/cm 2 .
17. The method of claim 16 wherein the read sensor has a track width of not more than thirty nanometers and wherein the rear soft magnetic bias structure has a width of at least thirty nanometers.
18. The method of claim 17 wherein the step of providing the rear magnetic bias structure further includes:
providing a rear hard magnetic bias structure, the rear soft magnetic bias structure being between the read sensor and the rear hard magnetic bias structure.
19. The method of claim 18 wherein the step of providing the read sensor further includes defining a read sensor stripe height and wherein the step of providing the rear magnetic bias structure further includes:
depositing at least one soft magnetic bias structure layer;
defining a depth of the at least one soft magnetic bias structure; and
depositing at least one hard bias layer for the rear hard magnetic bias structure.
20. The method of claim 19 further comprising:
providing a bottom shield;
providing a top shield, the read sensor residing between the bottom shield and the top shield; and wherein the step of providing the rear magnetic bias structure further includes:
magnetically coupling the rear soft bias magnetic structure to the bottom shield or the top shield.
21. The method of claim 16 wherein the side bias structure further includes a first magnetic structure, a second magnetic structure and a nonmagnetic structure between the first magnetic structure and the second magnetic structure, the first magnetic structure and the second magnetic structure being antiferromagnetically aligned.