Magnetoresistive sensor with overlapping leads having distributed current
View Patent ↗Magnetoresistive (MR) sensors have leads that overlap a MR structure and distribute current to the MR structure so that the current is not concentrated in small portions of the leads. An electrically resistive capping layer can be formed between the leads and the MR structure to distribute the current. The leads can include resistive layers and conductive layers, the resistive layers having a thickness-to-resistivity ratio that is greater than that of each of the conductive layers. The resistive layers may protect the conductive layers during MR structure etching, so that the leads have broad layers of electrically conductive material for connection to MR structures. The broad leads conduct heat better than the read gap material that they replace, further reducing the temperature at the connection between the leads and the MR structure.
1. A device comprising:
a magnetoresistive structure having a first edge and a second edge that are separated in a track-width direction by a first distance;
a first bias layer adjoining said first edge;
a second bias layer adjoining said second edge;
a first lead layer disposed adjacent to said first bias layer and overlapping said first edge; and
a second lead layer disposed adjacent to said second bias layer and overlapping said second edge;
wherein said first and second lead layers are separated from each other in said track-width direction by a second distance that is less than said first distance, said first lead layer including a resistive layer and a conductive layer, the resistive layer having a resistivity greater than 10 −7 Ωm at 25° C. and a greatest thickness larger than half that of said first lead layer, the conductive layer having a thickness to resistivity ratio that is not more than about that of the resistive layer and a conductive layer resistivity less than 10 −7 Ωm.
2. The device of claim 1 , further comprising a capping layer disposed between said magnetoresistive structure and said first and second lead layers, said capping layer having a thickness that is greater in first and second regions disposed adjacent to said first and second edges, respectively, than in a third region disposed between said first and second regions.
3. The device of claim 2 , wherein said first and second regions have a resistivity that is less than that of said third region.
4. The device of claim 1 , further comprising a capping layer disposed between said magnetoresistive structure and said first and second lead layers, said capping layer having a resistivity greater than 10 −7 Ωm at 25° C.
5. The device of claim 1 , wherein said device has a media-facing surface, and said first and second lead layers extend further than said magnetoresistive structure from said media-facing surface.
6. The device of claim 1 , wherein said first and second lead layers each include a layer of chromium having a thickness that is greater than 250 Å.
7. The device of claim 1 , wherein the conductive layer has a thickness-to-resistivity ratio that is about equal that of said resistive layer.
8. The device of claim 1 , wherein said magnetoresistive structure includes a first ferromagnetic layer separated from a second ferromagnetic layer by an electrically conductive, nonmagnetic spacer layer, said first ferromagnetic layer having a magnetization direction that is substantially fixed in the presence of an applied magnetic field, said second ferromagnetic layer having a magnetization direction that varies in response to said applied magnetic field.
9. A device comprising:
a magnetoresistive structure disposed adjacent to a media-facing surface and having a first edge and a second edge that are separated by a first distance in a track-width direction;
a first bias layer adjoining said first edge and a second bias layer adjoining said second edge; and
a first lead layer disposed adjacent to said first bias layer and extending beyond said first edge to overlap said magnetoresistive structure in a portion of a first region, and a second lead layer disposed adjacent to said second bias layer and extending beyond said second edge to overlap said magnetoresistive structure in a portion of a second region, said first and second regions separated from each other in said track-width direction by a second distance that is less than said first distance, said first and second regions extending further than said magnetoresistive structure from said media-facing surface, said first lead layer including a resistive layer having a resistive layer thickness and a resistive layer resistivity, said first lead layer including a conductive layer having a conductive layer thickness and a conductive layer resistivity, the conductive layer resistivity being less than 10 −7 Ωm;
wherein a ratio of said resistive layer thickness to said resistive layer resistivity is greater than or about equal to a ratio of said conductive layer thickness to said conductive layer resistivity.
10. The device of claim 9 , further comprising a capping layer disposed between said magnetoresistive structure and said first and second lead layers, said capping layer having a thickness that is greater in said first and second regions than in a third region disposed between said first and second regions.
11. The device of claim 10 , wherein said third region has a resistivity that is greater than that of said first and second regions.
12. The device of claim 9 , wherein said first and second lead layers include a material having a resistivity less than 6×10 −8 Ωm at 25° C.
13. The device of claim 9 , wherein said first and second lead layers include a material having a resistivity greater than 10 −7 Ωm at 25° C.
14. The device of claim 9 , wherein said second lead layer includes plural resistive layers and plural conductive layers, said resistive layers each having a thickness-to-resistivity ratio that is greater than that of each of said conductive layers.
15. The device of claim 9 , wherein said magnetoresistive structure includes a first ferromagnetic layer separated from a second ferromagnetic layer by an electrically conductive, nonmagnetic spacer layer, said first ferromagnetic layer having a magnetization direction that is substantially fixed in the presence of an applied magnetic field, said second ferromagnetic layer having a magnetization direction that varies in response to said applied magnetic field.