Magnetoresistive sensor with improved magnetic properties and magnetostriction control
A free layer comprising a bilayer (e.g., a first and a second layer) with an amorphous insertion layer in between the bilayer. The free layer includes a ferromagnetic nanolayer between the bilayer and a barrier layer. The magnetostriction of the free layer is tunable by varying the thicknesses of each of the first and the second layers. The free layer can be part of a magnetoresistive device with a reference layer or with another free layer.
1. A magnetoresistive device, comprising:
a barrier layer;
a free layer over the barrier layer, the free layer comprising:
a ferromagnetic nanolayer on the barrier layer;
a first layer proximate the barrier layer and over the ferromagnetic nanolayer;
a second layer away from the barrier layer and over the first layer; and
an amorphous insertion layer between the first layer and the second layer; and
a non-ferromagnetic capping layer over the free layer,
wherein each of the first layer and the second layer independently comprises a material selected from CoFeB and CoB,
wherein the first layer has a thickness from about 1.5 times to about 10 times a thickness of the second layer.
2. The magnetoresistive device of claim 1 , wherein the free layer has a thickness of about 100 Å or less.
3. The magnetoresistive device of claim 1 , wherein the amorphous insertion layer comprises CoHf.
4. The magnetoresistive device of claim 1 , wherein the ferromagnetic nanolayer comprises CoFe.
5. The magnetoresistive device of claim 1 , wherein each of the first layer and the second layer independently comprises CoFeB with Fe in an atomic percent of about 60% or less.
6. The magnetoresistive device of claim 1 , wherein the first layer has a thickness from about 1.5 times to about 3 times larger than a thickness of the second layer.
7. A magnetic media drive comprising a read sensor comprising the magnetoresistive device of claim 1 .
8. A magnetoresistive device, comprising:
a seed layer;
a buffer layer over the seed layer;
a first free layer over the buffer layer,
a barrier layer over the first free layer;
a second free layer over the barrier layer;
the first free layer comprising:
a ferromagnetic nanolayer adjacent the barrier layer;
a first layer proximate the barrier layer; and
a second layer away from the barrier layer; and
an insertion layer between the first layer and the second layer; and
the second free layer comprising:
a ferromagnetic nanolayer on the barrier layer;
a first layer proximate the barrier layer; and
a second layer away from the barrier layer; and
an insertion layer between the first layer and the second layer; and
a non-ferromagnetic capping layer over the second free layer,
wherein the first layer of the first free layer has a thickness from about 0.1 times to about 10 times a thickness of the second layer of the first free layer,
wherein the first layer of the second free layer has a thickness from about 0.1 times to about 10 times a thickness of the second layer of the second free layer,
wherein each of the first layer and the second layer of each of the first free layer and the second free layer independently comprises a material selected from CoFeB and CoB.
9. The magnetoresistive device of claim 8 , wherein the first free layer and the second free layer each independently has a thickness of about 100 Å or less.
10. The magnetoresistive device of claim 8 , wherein the insertion layer of each of the first free layer and the second free layer comprises CoHf.
11. The magnetoresistive device of claim 8 , wherein the ferromagnetic nanolayer each of the first free layer and the second free layer comprises CoFe.
12. The magnetoresistive device of claim 8 , each of the first layer and the second layer of each of the first free layer and the second free layer independently comprises CoFeB with Fe in an atomic percent of about 60% or less.
13. The magnetoresistive device of claim 8 , wherein the first layer of the first free layer has a thickness from about 1.5 times to about 3 times larger than a thickness of the second layer of the first free layer, and
wherein the first layer of the second free layer has a thickness from about 1.5 times to about 3 times larger than a thickness of the second layer of the second free layer.
14. A magnetic media drive comprising a read sensor comprising the magnetoresistive device of claim 8 .
15. A magnetoresistive device, comprising:
a MgO barrier layer;
a free layer over the MgO barrier layer, the free layer comprising:
a CoFe nanolayer on the MgO barrier layer;
a first layer proximate the MgO barrier layer and over the CoFe nanolayer;
a second layer away from the MgO barrier layer and over the first layer; and
a CoHf insertion layer between the first layer and the second layer; and
a capping layer over the free layer,
wherein each of the first layer and the second layer independently comprises a material selected from CoFeB having an atomic percent of Fe of about 60% or less and CoB having an atomic percentage of B of about 5% to about 50%,
wherein the first layer has a thickness from about 0.1 times to about 10 times a thickness of the second layer,
wherein the free layer has a thickness of about 100 Å or less.
16. The magnetoresistive device of claim 15 , wherein the first layer has a thickness from about 1.5 times to about 3 times larger than a thickness of the second layer.
17. The magnetoresistive device of claim 15 , wherein the free layer has a magnetic saturation moment (Bs) of about 1 Tesla or greater.
18. The magnetoresistive device of claim 15 , wherein the free layer has a coercivity (Hc) of about 3 Oe or less and with an induced coupling (Hint) of 150 Oe or less.
19. The magnetoresistive device of claim 15 , wherein the free layer has a magnetostriction of an absolute value of 5×10 −7 or less.
20. A magnetic media drive comprising a read sensor comprising the magnetoresistive device of claim 15 .