Slider with spin-torque oscillator (STO) and STO corrosion monitor
A disk drive slider supports a microwave-assisted magnetic recording (MAMR) write head with a spin-torque oscillator (STO) and a separate corrosion monitor (CM). The CM includes a corrosion detection layer formed of the same material as the STO's spacer layer. The CM is coplanar with the STO but laterally spaced from the STO. The corrosion detection layer has an edge at the ABS so as to be exposed to the same atmospheric conditions as the STO's spacer layer. Electrical leads are located at the ends of the CM and are electrically connected to pads on the upper surface of the slider. Electrical resistance of the CM is measured by detection of current in the plane of the corrosion detection layer.
1. A slider having a trailing surface, a plurality of layers on the trailing surface, an upper surface substantially parallel to the trailing surface and an air-bearing surface (ABS) substantially orthogonal to the trailing surface, the slider comprising:
a write head on the trailing surface including a write pole and a trailing shield;
a spin torque oscillator (STO) between the write sole and the trailing shield, the STO having an electrically conductive spacer layer adapted to receive electrical current in a direction orthogonal to the plane of the spacer layer;
a corrosion monitor (CM) on the trailing surface and laterally spaced from the STO so as to not be located between the write pole and the trailing shield, the CM having a corrosion detection layer formed of the same material as said spacer layer;
a first electrically conductive lead connected to a first end of the corrosion detection layer;
a second electrically conductive lead connected to a second end of the corrosion detection layer, the first and second leads adapted to direct electrical current between the first and second ends of the corrosion detection layer in a direction parallel to the plane of the corrosion detection layer;
a first contact pad on the upper surface of the slider and electrically connected to said first lead; and
a second contact pad on the upper surface of the slider and electrically connected to said second lead.
2. The slider of claim 1 wherein the CM is substantially coplanar with the STO.
3. The slider of claim 1 wherein the corrosion detection layer has a thickness substantially the same as the thickness of said spacer layer.
4. The slider of claim 1 wherein said spacer layer has an edge substantially at the ABS and said corrosion detection layer has an edge substantially at the ABS.
5. The slider of claim 4 wherein said corrosion detection layer edge has a width at least 10 times the width of said spacer layer edge.
6. The slider of claim 1 wherein the STO includes a ferromagnetic reference layer and a ferromagnetic field generating layer (FGL) and said spacer layer is located between said reference and FGL layers, and wherein the CM includes a first ferromagnetic layer formed of the same material as said reference layer and a second ferromagnetic layer formed of the same material as said FGL layer and wherein the corrosion detection layer is located between said first and second ferromagnetic layers.
7. The slider of claim 1 wherein said spacer layer is formed of a material selected from Cu, CuZn, CuSn, CuAl and CuNi.
8. The slider of claim 7 wherein the spacer layer material consists of Cu.
9. The slider of claim 1 further comprising a first electrically conductive via connecting said first contact pad on the upper surface to said first lead and a second electrically conductive via connecting said second contact pad on the upper surface to said second lead.
10. A slider having a trailing surface, an upper surface parallel to the trailing surface, an intermediate surface parallel to the trailing surface and between the trailing surface and the upper surface, and an air-bearing surface (ABS) substantially orthogonal to the trailing surface, the slider comprising:
a spin torque oscillator (STO) on the intermediate surface, the STO having an electrically conductive spacer layer having an edge at the ABS;
a corrosion monitor (CM) on the intermediate surface and laterally spaced from the STO, the CM having a corrosion detection layer formed of the same material as said spacer layer and having an edge at the ABS with a width at least 10 times the width of said spacer layer edge;
a first electrically conductive lead connected to a first end of the CM;
a second electrically conductive lead connected to a second end of the CM;
a first contact pad on the upper surface of the slider and electrically connected to said first lead; and
a second contact pad on the upper surface of the slider and electrically connected to said second lead.
11. The slider of claim 10 wherein the corrosion detection layer has a thickness substantially the same as the thickness of said spacer layer.
12. The slider of claim 10 wherein the STO includes a ferromagnetic reference layer and a ferromagnetic field generating layer (FGL) and said spacer layer is located between said reference and FGL layers, and wherein the CM includes a first ferromagnetic layer formed of the same material as said reference layer and a second ferromagnetic layer formed of the same material as said FGL layer and wherein the corrosion detection layer is located between said first and second ferromagnetic layers.
13. The slider of claim 10 wherein said spacer layer is formed of a material selected from Cu, CuZn, CuSn, CuAl and CuNi.