Tunneling magnetoresistance read sensor with dual sense layers
View Patent ↗A tunneling magnetoresistance (TMR) read sensor with a Co—Fe—B lower sense layer and a Co—Hf upper sense layer is disclosed. In order for the dual sense layers to exhibit a negative saturation magnetostriction (λ S ), their Fe contents are either substantially reduced or even eliminated, instead of adding a conventional Ni—Fe film as an additional sense layer. By optimizing compositions and thicknesses of the dual sense layers, the dual sense layers indeed exhibit a negative λ S , while the TMR sensor exhibits a TMR coefficient (ΔR T /R J ) of greater than 80% at a junction resistance-area product (R J A J ) of less than 2 Ω-μm 2 .
1. A thin film magnetic head having a TMR read sensor comprising:
a magnesium oxide barrier layer;
a lower sense layer, comprising a Co—Fe—B alloy, deposited on said magnesium oxide barrier layer;
an upper sense layer, comprising a Co—Hf alloy, deposited on said lower sense layer; and
a cap layer deposited on said upper sense layer, wherein said TMR read sensor has a saturation magnetostiction value less than zero, a resistance-area product less than 2.5 W-μm 2 , and a TMR coefficient greater than 75%.
2. The magnetic head as recited in claim 1 , wherein said upper sense layer comprises an alloy containing between 84 and 85 atomic % Co, and between 15 and 16 atomic % Hf.
3. The magnetic head as recited in claim 2 , wherein said lower sense layer comprises an alloy containing between 71 and 86 atomic % Co, between 8 and 3 atomic % Fe, and between 11 and 22 atomic % B.
4. The magnetic head as recited in claim 3 , wherein said lower sense layer comprises an alloy containing between 79 and 86 atomic % Co, between 5 and 3 atomic % Fe, and between 11 and 15 atomic % B.
5. The magnetic head as recited in claim 1 , wherein said lower sense layer comprises an alloy containing between 71 and 86 atomic % Co, between 8 and 3 atomic % Fe, and between 11 and 22 atomic % B.
6. The magnetic head as recited in claim 5 , wherein said lower sense layer comprises an alloy containing between 79 and 86 atomic % Co, between 5 and 3 atomic % Fe, and between 11 and 15 atomic % B.
7. The magnetic head as recited in claim 1 , wherein said upper sense layer is between 0.5 and 5 nm in thickness.
8. The magnetic head as recited in claim 7 , wherein said upper sense layer is between 0.5 and 2.5 nm in thickness.
9. The magnetic head as recited in claim 2 , wherein said upper sense layer is between 0.5 and 2.5 nm in thickness.
10. The magnetic head as recited in claim 1 , wherein said lower sense layer is between 0.5 and 4 nm in thickness.
11. The magnetic head as recited in claim 10 , wherein said lower sense layer is between 1.3 and 2.5 nm in thickness.
12. The magnetic head as recited in claim 4 , wherein said lower sense layer is between 1.3 and 2.5 nm in thickness.
13. A thin film magnetic head having a TMR read sensor comprising:
a magnesium oxide barrier layer;
a lower sense layer, comprising a Co—Fe—B alloy, deposited on said magnesium oxide barrier layer, said Co—Fe—B alloy having a Co composition between 71 and 86 atomic %, an Fe composition between 8 and 3 atomic %, and a B composition between 11 and 22 atomic %;
an upper sense layer, comprising a Co—Hf alloy, deposited on said lower sense layer, said Co—Hf alloy having a Co composition between 84 and 85 atomic %; and
a cap layer deposited on said upper sense layer,
wherein said TMR read sensor has a saturation magnetostiction value less than zero, a resistance-area product less than 2 W-μm 2 , and a TMR coefficient greater than 80%.
14. The magnetic head as recited in claim 13 , wherein said lower sense layer comprises an alloy containing between 79 and 86 atomic % Co, between 5 and 3 atomic % Fe, and between 11 and 15 atomic % B.
15. The magnetic head as recited in claim 13 , wherein said upper sense layer is between 0.5 and 5 nm in thickness.
16. The magnetic head as recited in claim 15 , wherein said upper sense layer is between 0.5 and 2.5 nm in thickness.
17. The magnetic head as recited in claim 13 , wherein said lower sense layer is between 0.5 and 4 nm in thickness.
18. The magnetic head as recited in claim 17 , wherein said lower sense layer is between 1.3 and 2.5 nm in thickness.
19. A thin film magnetic head having a TMR read sensor comprising:
a magnesium oxide barrier layer;
a lower sense layer, comprising a Co—Fe—B alloy, deposited on said magnesium oxide barrier layer, said Co—Fe—B alloy having a Co composition between 79 and 86 atomic %, an Fe composition between 5 and 3 atomic %, and a B composition between 11 and 15 atomic %;
an upper sense layer, comprising a Co—Hf alloy, deposited on said lower sense layer, said Co—Hf alloy having a Co composition between 84 and 85 atomic %; and
a cap layer deposited on said upper sense layer,
wherein said TMR read sensor has a saturation magnetostiction value less than zero, a resistance-area product less than 2 W-μm 2 , and a TMR coefficient greater than 80%.
20. The magnetic head as recited in claim 19 , wherein said upper sense layer is between 0.5 and 2.5 nm in thickness.
21. The magnetic head as recited in claim 19 , wherein said lower sense layer is between 1.3 and 2.5 nm in thickness.