Magnetic sensor with underlayers promoting high-coercivity, in-plane bias layers
View Patent ↗A magnetic sensor is disclosed comprising an antiferromagnetic layer; a first ferromagnetic layer disposed over the antiferromagnetic layer, the first ferromagnetic layer having a magnetization that is pinned by the antiferromagnetic layer; a second ferromagnetic layer disposed over the first ferromagnetic layer, the second ferromagnetic layer having a magnetization that rotates due to an applied magnetic field; a third ferromagnetic layer disposed adjacent to an end of the second ferromagnetic layer, the third ferromagnetic layer having a primarily in-plane magnetization providing a magnetic field to stabilize the end of the second ferromagnetic layer; an amorphous, metallic, nonmagnetic underlayer disposed adjacent to the antiferromagnetic layer; and a crystalline seed layer disposed between the underlayer and the third ferromagnetic layer, the seed layer having a crystalline structure that promotes the in-plane magnetization of the third ferromagnetic layer.
1. A magnetic sensor comprising:
an antiferromagnetic layer;
a first ferromagnetic layer disposed over the antiferromagnetic layer, the first ferromagnetic layer having a magnetization that is pinned by the antiferromagnetic layer;
a second ferromagnetic layer disposed over the first ferromagnetic layer, the second ferromagnetic layer having a magnetization that rotates due to an applied magnetic field;
a third ferromagnetic layer disposed adjacent to an end of the second ferromagnetic layer, the third ferromagnetic layer having a primarily in-plane magnetization providing a magnetic field to stabilize the end of the second ferromagnetic layer;
an amorphous, metallic, nonmagnetic underlayer disposed adjacent to the antiferromagnetic layer; and
a crystalline seed layer disposed between the underlayer and the third ferromagnetic layer, the seed layer having a crystalline structure that promotes the in-plane magnetization of the third ferromagnetic layer.
2. The sensor of claim 1 , wherein the underlayer isolates the third ferromagnetic layer from the crystalline structure of the antiferromagnetic layer.
3. The sensor of claim 1 , wherein the underlayer includes gallium or tantalum.
4. The sensor of claim 1 , wherein the underlayer includes elements X and Y, wherein X is selected from the group consisting of nickel, cobalt, iron, copper or aluminum, and Y is selected from the group consisting of niobium, phosphorous, zirconium, hafnium, tantalum, gallium, terbium, bismuth or dysprosium.
5. The sensor of claim 1 , wherein the underlayer includes nickel-niobium.
6. The sensor of claim 1 , wherein the seed layer includes chromium.
7. The sensor of claim 1 , wherein the seed layer is a chromium alloy, and includes an element selected from the group consisting of titanium, vanadium, molybdenum, manganese or tungsten.
8. The sensor of claim 1 , wherein the seed layer has a body-centered cubic (bcc) crystalline structure.
9. The sensor of claim 1 , wherein the seed layer has a B2 crystalline structure.
10. The sensor of claim 1 , wherein the seed layer is made of a tungsten alloy, and includes an element selected from the group consisting of titanium, vanadium, molybdenum or chromium.
11. The sensor of claim 1 , wherein the seed layer includes tungsten.
12. The sensor of claim 1 , wherein the seed layer includes an atomic concentration of chromium that is between fifty percent and ninety-five percent.
13. The sensor of claim 1 , wherein the seed layer has a crystalline structure that is approximately lattice matched with that of the third ferromagnetic layer.
14. The sensor of claim 1 , wherein the seed layer includes nickel-aluminum.
15. The sensor of claim 1 , wherein the antiferromagnetic layer includes manganese.
16. The sensor of claim 1 , wherein the third ferromagnetic layer includes cobalt.
17. The sensor of claim 1 , wherein the antiferromagnetic layer extends more than twice as far as the free layer in a track width direction.
18. A magnetic sensor comprising:
an antiferromagnetic layer having a crystalline structure;
a pinned ferromagnetic layer disposed over the antiferromagnetic layer;
a free ferromagnetic layer disposed over the pinned ferromagnetic layer, the free ferromagnetic layer having a magnetization that rotates due to an applied magnetic field;
a pair of magnetically hard bias layers disposed adjacent to opposite ends of the free ferromagnetic layer, the bias layers having a primarily in-plane magnetization providing a magnetic field to stabilize the ends of the free ferromagnetic layer;
a pair of amorphous, metallic, nonmagnetic underlayers disposed adjacent to the antiferromagnetic layer to isolate the crystalline structure of the antiferromagnetic layer; and
a pair of crystalline seed layers, each of the seed layers disposed between one of the underlayers and one of the bias layers to promote the in-plane magnetization of the bias layers.
19. The sensor of claim 18 , wherein the underlayers include nickel-niobium.
20. The sensor of claim 18 , wherein the underlayers include gallium or tantalum.
21. The sensor of claim 18 , wherein the underlayer includes elements X and Y, wherein X is selected from the group consisting of nickel, cobalt, iron, copper or aluminum, and Y is selected from the group consisting of niobium, phosphorous, zirconium, hafnium, tantalum, gallium, terbium, bismuth or dysprosium.
22. The sensor of claim 18 , wherein the seed layer includes chromium.
23. The sensor of claim 18 , wherein the seed layers are made of a chromium alloy, and include an element selected from the group consisting of titanium, vanadium, molybdenum, manganese or tungsten.
24. The sensor of claim 18 , wherein the seed layers are made of a tungsten alloy, and include an element selected from the group consisting of titanium, vanadium, molybdenum or chromium.
25. The sensor of claim 18 , wherein the seed layers include tungsten.
26. The sensor of claim 18 , wherein the seed layers include a body-centered-cubic (bcc) crystalline structure.
27. The sensor of claim 18 , wherein the seed layers include a B2 crystalline structure.
28. The sensor of claim 18 , wherein the seed layers include an atomic concentration of chromium that is between fifty percent and ninety-five percent.
29. The sensor of claim 18 , wherein the seed layers have a crystalline structure that is approximately lattice matched with that of the bias layers.
30. The sensor of claim 18 , wherein the seed layer includes nickel-aluminum.
31. The sensor of claim 18 , wherein the antiferromagnetic layer includes manganese.
32. The sensor of claim 18 , wherein the bias layers include cobalt.
33. The sensor of claim 18 , wherein the antiferromagnetic layer extends more than twice as far as the free layer in a track width direction.
34. A magnetic sensor comprising:
an antiferromagnetic layer having a crystalline structure;
a pinned ferromagnetic layer disposed over the antiferromagnetic layer;
a free ferromagnetic layer disposed over the pinned ferromagnetic layer, the free ferromagnetic layer having a magnetization that rotates due to an applied magnetic field;
a pair of amorphous, metallic, nonmagnetic underlayers disposed adjacent to the antiferromagnetic layer to isolate the crystalline structure of the antiferromagnetic layer;
a pair of crystalline seed layers, each of the seed layers disposed over one of the underlayers; and
a pair of magnetically hard bias layers disposed adjacent to opposite ends of the free ferromagnetic layer, each of the bias layers grown on one of the seed layers to have a primarily in-plane magnetization providing a magnetic field to stabilize the ends of the free ferromagnetic layer.
35. The sensor of claim 34 , wherein the underlayers include nickel-niobium.
36. The sensor of claim 34 , wherein the underlayers include gallium or tantalum.
37. The sensor of claim 34 , wherein the underlayer includes elements X and Y, wherein X is selected from the group consisting of nickel, cobalt, iron, copper or aluminum, and Y is selected from the group consisting of niobium, phosphorous, zirconium, hafnium, tantalum, gallium, terbium, bismuth or dysprosium.
38. The sensor of claim 34 , wherein the seed layers are made of a chromium alloy, and include an element selected from the group consisting of titanium, vanadium, molybdenum, manganese or tungsten.
39. The sensor of claim 34 , wherein the seed layers are made of a tungsten.
40. The sensor of claim 34 , wherein the seed layers are made of a tungsten alloy, and include an element selected from the group consisting of titanium, vanadium, molybdenum or chromium.
41. The sensor of claim 34 , wherein the seed layers include a body-centered-cubic (bcc) crystalline structure.
42. The sensor of claim 34 , wherein the seed layers include a B2 crystalline structure.
43. The sensor of claim 34 , wherein the seed layers include an atomic concentration of chromium that is between fifty percent and ninety-five percent.
44. The sensor of claim 34 , wherein the seed layers have a crystalline structure that is not lattice matched with the that of the antiferromagnetic layer.
45. The sensor of claim 34 , wherein the seed layer includes nickel-aluminum.
46. The sensor of claim 34 , wherein the antiferromagnetic layer includes manganese.
47. The sensor of claim 34 , wherein the bias layers include cobalt.
48. The sensor of claim 34 , wherein the antiferromagnetic layer extends more than twice as far as the free layer in a track width direction.