Magnetoresistive element including ferromagnetic sublayer having smoothed surface

1. A magnetoresistive element comprising:

a pinned ferromagnetic layer;

a sense ferromagnetic layer; and

a spacer layer between the ferromagnetic layers;

the pinned layer including an amorphous sublayer and a crystalline sublayer, the crystalline sublayer between the amorphous sublayer and the spacer layer, the amorphous sublayer having a smoothed surface.

2. The element of claim 1 , wherein the smoothed surface has a valley-to-peak height difference of no more than about one nanometer.

3. The element of claim 2 , wherein angle from the top of a grain to an intersection with an adjacent grain is between about three and six degrees.

4. The element of claim 1 wherein the pinned layer further includes a second crystalline ferromagnetic sublayer, the amorphous ferromagnetic layer sandwiched between the two crystalline ferromagnetic sublayers.

5. The element of claim 1 , further comprising an antiferromagnetic pinning layer including manganese; wherein the pinned layer is on the antiferromagnetic layer; and wherein the pinned layer is smoothed to adjust antiferromagnetic coupling between the antiferromagnetic and pinned layers.

6. A read head for a data storage device, the read head comprising the element recited in claim 1 .

7. A data storage device comprising an array of memory cells, each memory cell including at least one element recited in claim 1 .

8. A method of fabricating the element recited in claim 1 , the method comprising:

depositing the amorphous ferromagnetic sublayer;

ion etching an exposed surface of the amorphous ferromagnetic sublayer to a critical flatness; and

depositing the crystalline ferromagnetic sublayer on the Ion etched surface of the amorphous ferromagnetic layer.

9. The element of claim 1 , wherein the smoothed surface of the amorphous sublayer has a critical flatness.

10. The element of claim 1 , wherein the surface of the amorphous sublayer is smoothed to improve grain structure of the sense ferromagnetic layer.

11. The element of claim 1 , wherein the pinned layer is smoothed to reduce ferromagnetic coupling.

12. A ferromagnetic layer for a magnetoresistive device, the layer comprising:

an amorphous ferromagnetic sublayer having a surface with a critical flatness; and

a second sublayer of a ferromagnetic material having a polarization and magnetic moment that are higher than the polarization and magnetic moment of the amorphous sublayer, the second sublayer on the surface with a critical flatness.

13. The layer of claim 12 , wherein a surface of the second sublayer is smoothed.

14. The layer of claim 13 , wherein the surface of the second sublayer is smoothed to a valley-to-peak height difference of no more than about one nanometer.

15. The layer of claim 10 , wherein the ferromagnetic layer is a pinned layer.

16. The layer of claim 12 , further comprising a third sublayer the third sublayer having a polarization and magnetic moment that are higher than the polarization and magnetic moment of the amorphous sublayer, the amorphous ferromagnetic sublayer sandwiched between the second and third sublayers.