Magnetoresistive element having a pair of side shields
An MR element includes an MR stack disposed between first and second main shield portions, and a pair of side shields disposed on opposite sides of the MR stack in the track width direction. The first main shield portion includes a first exchange coupling shield layer that is exchange-coupled to a first antiferromagnetic layer. The second main shield portion includes a second exchange coupling shield layer that is exchange-coupled to a second antiferromagnetic layer. The MR stack includes a spacer layer, and first and second free layers with the spacer layer therebetween. The direction of magnetization of the first free layer is controlled by the first exchange coupling shield layer. The direction of magnetization of the second free layer is controlled by the second exchange coupling shield layer. Each side shield includes at least one shield-coupling magnetic layer that is in contact with and magnetically coupled to one of the first and second exchange coupling shield layers.
1. A magnetoresistive element intended for detecting a magnetic signal written on a track of a recording medium, comprising:
a first main shield portion and a second main shield portion; and
an MR stack disposed between the first and second main shield portions, wherein:
the first main shield portion, the MR stack, and the second main shield portion are arranged in a direction in which the track extends;
the first main shield portion includes: a first main shield layer; a first antiferromagnetic layer that is disposed between the first main shield layer and the MR stack; and a first exchange coupling shield layer that is disposed between the first antiferromagnetic layer and the MR stack and is exchange-coupled to the first antiferromagnetic layer;
the second main shield portion includes: a second main shield layer; a second antiferromagnetic layer that is disposed between the second main shield layer and the MR stack; and a second exchange coupling shield layer that is disposed between the second antiferromagnetic layer and the MR stack and is exchange-coupled to the second antiferromagnetic layer;
the MR stack includes: a spacer layer made of a nonmagnetic material; a first free layer disposed between the first exchange coupling shield layer and the spacer layer; and a second free layer disposed between the second exchange coupling shield layer and the spacer layer;
the first free layer is magnetically coupled to the first exchange coupling shield layer, whereby a direction of magnetization of the first free layer is controlled; and
the second free layer is magnetically coupled to the second exchange coupling shield layer, whereby a direction of magnetization of the second free layer is controlled,
the magnetoresistive element further comprising a pair of side shields disposed on opposite sides of the MR stack in a track width direction, between the first main shield portion and the second main shield portion,
wherein each of the pair of side shields includes at least one shield-coupling magnetic layer that is in contact with and magnetically coupled to one of the first and second exchange coupling shield layers.
2. The magnetoresistive element according to claim 1 , wherein the MR stack and the second main shield portion are stacked in this order on the first main shield portion,
the magnetoresistive element further comprising a pair of insulating layers disposed between the first exchange coupling shield layer and the pair of side shields,
wherein the at least one shield-coupling magnetic layer is in contact with and magnetically coupled to the second exchange coupling shield layer.
3. The magnetoresistive element according to claim 2 , wherein top surfaces of the at least one shield-coupling magnetic layer and the MR stack are flattened.
4. The magnetoresistive element according to claim 3 , further comprising a pair of nonmagnetic layers disposed between the at least one shield-coupling magnetic layer and the pair of insulating layers.
5. The magnetoresistive element according to claim 4 , wherein the at least one shield-coupling magnetic layer is made of NiFe, and the nonmagnetic layers are made of a material selected from the group consisting of Cr, CrTi, and Ru.
6. The magnetoresistive element according to claim 4 , wherein a ratio of a thickness of the shield-coupling magnetic layer to a total thickness of the shield-coupling magnetic layer and the nonmagnetic layer is in the range of 13% to 87%.
7. The magnetoresistive element according to claim 1 , wherein the MR stack and the second main shield portion are stacked in this order on the first main shield portion,
the magnetoresistive element further comprising a pair of insulating layers disposed between the second exchange coupling shield layer and the pair of side shields,
wherein the at least one shield-coupling magnetic layer is in contact with and magnetically coupled to the first exchange coupling shield layer.
8. The magnetoresistive element according to claim 1 , wherein:
each of the pair of side shields includes a side shield middle layer that is made of a nonmagnetic conductive material, and first and second side shield magnetic layers that are antiferromagnetically exchange-coupled to each other via the side shield middle layer; and
one of the first and second side shield magnetic layers is the at least one shield-coupling magnetic layer.
9. The magnetoresistive element according to claim 8 , wherein the MR stack and the second main shield portion are stacked in this order on the first main shield portion,
the magnetoresistive element further comprising a pair of insulating layers disposed between the first exchange coupling shield layer and the pair of side shields,
wherein the side shield middle layer and the second side shield magnetic layer are stacked in this order on the first side shield magnetic layer, and
the second side shield magnetic layer is the at least one shield-coupling magnetic layer, and is in contact with and magnetically coupled to the second exchange coupling shield layer.
10. The magnetoresistive element according to claim 1 , wherein:
each of the pair of side shields includes first and second side shield magnetic layers, and a side shield insulating layer that is disposed between the first and second side shield magnetic layers;
both of the first and second side shield magnetic layers are the at least one shield-coupling magnetic layer;
the first side shield magnetic layer is in contact with and magnetically coupled to the first exchange coupling shield layer; and
the second side shield magnetic layer is in contact with and magnetically coupled to the second exchange coupling shield layer.
11. The magnetoresistive element according to claim 1 , wherein:
one of the first and second exchange coupling shield layers includes a shield middle layer that is made of a nonmagnetic conductive material, and two ferromagnetic layers that are antiferromagnetically exchange-coupled to each other via the shield middle layer; and
the other of the first and second exchange coupling shield layers includes one or more ferromagnetic layers and no shield middle layer.
12. A thin-film magnetic head comprising the magnetoresistive element according to claim 1 , the thin-film magnetic head having a medium facing surface that faces the recording medium, the magnetoresistive element being disposed near the medium facing surface.
13. A head assembly comprising a slider, and a supporter that flexibly supports the slider, wherein the slider includes the thin-film magnetic head according to claim 12 and is disposed to face the recording medium.
14. A magnetic recording device comprising the thin-film magnetic head according to claim 12 , the recording medium, and a positioning device that supports the thin-film magnetic head and positions the thin-film magnetic head with respect to the recording medium.
15. A method of manufacturing the magnetoresistive element according to claim 1 , comprising the steps of:
forming the first main shield portion;
forming the MR stack and the pair of side shields after the formation of the first main shield portion; and
forming the second main shield portion after the formation of the MR stack and the pair of side shields.
16. The method according to claim 15 , wherein:
the magnetoresistive element further comprises a pair of insulating layers disposed between the first exchange coupling shield layer and the pair of side shields;
the at least one shield-coupling magnetic layer is in contact with and magnetically coupled to the second exchange coupling shield layer; and
the step of forming the MR stack and the pair of side shields includes the step of forming the pair of insulating layers and the step of flattening top surfaces of the at least one shield-coupling magnetic layer and the MR stack.
17. The method according to claim 16 , wherein:
the magnetoresistive element further comprises a pair of nonmagnetic layers disposed between the at least one shield-coupling magnetic layer and the pair of insulating layers; and
the step of forming the MR stack and the pair of side shields further includes the step of forming the pair of nonmagnetic layers.