Tunnel magnetoresistance read head including side shields containing nanocrystalline ferromagnetic particles
View Patent ↗A tunnel magnetoresistance (TMR) read head includes a first magnetic shield, a read sensor stripe located over the first magnetic shield, a second magnetic shield located over the sensor layer stack, an electrical isolation dielectric layer located on sidewalls of the read sensor stripe, and a pair of side shields located on the electrical isolation dielectric layer between the first magnetic shield and the second magnetic shield. The read sensor stripe includes a sensor layer stack containing a pinned layer stack, a non-magnetic electrically insulating barrier layer, and a ferromagnetic free layer. The side shields include nanocrystalline ferromagnetic particles, such as Fe, Co or CoFe, embedded in a non-magnetic dielectric material matrix, such as hafnium oxide.
1. A tunnel magnetoresistance (TMR) read head comprising:
a first magnetic shield;
a read sensor stripe located over the first magnetic shield, the read sensor stripe comprising a sensor layer stack comprising a pinned layer stack, a non-magnetic electrically insulating barrier layer, and a ferromagnetic free layer;
a second magnetic shield located over the sensor layer stack;
an electrical isolation dielectric layer located on sidewalls of the read sensor stripe; and
a pair of side shields located on the electrical isolation dielectric layer between the first magnetic shield and the second magnetic shield, and comprising nanocrystalline ferromagnetic particles embedded in a non-magnetic dielectric material matrix.
2. The TMR read head of claim 1 , wherein the non-magnetic dielectric material matrix comprises hafnium oxide and the nanocrystalline ferromagnetic particles comprise a material selected from iron particles, cobalt particles, and particles of an alloy of iron and cobalt.
3. The TMR read head of claim 2 , wherein the nanocrystalline ferromagnetic particles comprise the alloy of iron and cobalt having an atomic ratio of iron atoms to cobalt atoms in a range from 1/9 to 9.
4. The TMR read head of claim 2 , wherein the nanocrystalline ferromagnetic particles have a diameter of 3 nm to 10 nm and comprise body centered cubic lattice structure, and wherein the non-magnetic dielectric material matrix comprises amorphous hafnium oxide.
5. The TMR read head of claim 2 , wherein an atomic ratio of metal atoms in the nanocrystalline ferromagnetic particles to hafnium atoms within the pair of side shields is in a range from 1 to 9.
6. The TMR read head of claim 2 , wherein:
more than 90% of all hafnium atoms in the non-magnetic dielectric material matrix are in an oxidized state; and
more than 98% of all metal atoms in the nanocrystalline ferromagnetic particles are in an unoxidized state.
7. The TMR read head of claim 1 , wherein the non-magnetic dielectric material matrix comprises a material selected from aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, and tantalum oxide.
8. The TMR read head of claim 1 , wherein the pair of side shields is spaced from the first magnetic shield by a planar portion of the electrical isolation dielectric layer having a planar surface that is parallel to an interface between the first magnetic shield and the sensor layer stack.
9. The TMR read head of claim 8 , wherein the pair of side shields contacts a surface of the second magnetic shield that is parallel to the interface between the first magnetic shield and the sensor layer stack.
10. The TMR read head of claim 8 , wherein:
each of the pair of side shields contacts a respective tapered sidewall of the electrical isolation dielectric layer; and
the pair of side shields is spaced from the planar portion of the electrical isolation dielectric layer by a pair of nonmagnetic spacers.
11. The TMR read head of claim 1 , wherein:
the pinned layer stack comprising an antiferromagnetic pinning layer and at least one ferromagnetic pinned layer; and
the sensor layer stack further comprises a backside electrically conductive layer contacting the first magnetic shield, and a front side non-magnetic electrically conductive layer contacting the second magnetic shield.
12. A hard disk drive, comprising:
a magnetic head containing the TMR read head of claim 1 ;
a slider supporting the magnetic head;
an actuator arm supporting the slider;
a voice coil motor configured to control the actuator arm; and
a magnetic disk.
13. The hard disk drive of claim 12 , wherein a difference between an MT50 of the TMR read head and a free layer track width is less than 6.3 nm.
14. A method of forming a tunnel magnetoresistance (TMR) read head, comprising:
forming a sensor layer stack including a pinned layer stack, a non-magnetic electrically insulating barrier layer, and a ferromagnetic free layer over a first magnetic shield;
forming a read sensor stripe by patterning the sensor layer stack;
forming an electrical isolation dielectric layer over sidewalls of the read sensor stripe;
forming a pair of side shields over the electrical isolation dielectric layer and on both sides of the read sensor stripe, wherein the pair of side shields comprises nanocrystalline ferromagnetic particles embedded in a non-magnetic dielectric material matrix; and
forming a second magnetic shield over the sensor layer stack.
15. The method of claim 14 , wherein a combination of the nanocrystalline ferromagnetic particles and the non-magnetic dielectric material matrix is formed by a reactive ion beam sputtering process in which a target material including an alloy of hafnium and at least one magnetic element is sputtered over the electrical isolation dielectric layer by an argon ion beam in an oxygen-containing ambient.
16. The method of claim 15 , wherein:
the non-magnetic dielectric material matrix comprises hafnium oxide;
the at least one magnetic element is selected from iron, cobalt, and a combination of iron and cobalt; and
the nanocrystalline ferromagnetic particles comprise a material selected from iron particles, cobalt particles, and particles of an alloy of iron and cobalt.
17. The method of claim 16 , wherein:
the nanocrystalline ferromagnetic particles comprise the alloy of iron and cobalt;
an atomic ratio of iron atoms to cobalt atoms within the alloy of iron and cobalt range from 1/9 to 9; and
an atomic ratio of the at least one magnetic element to hafnium atoms within target material is in a range from 1 to 9.
18. The method of claim 16 , wherein:
more than 90% of all hafnium atoms in the non-magnetic dielectric material matrix are in an oxidized state; and
more than 98% of all metal atoms in the nanocrystalline ferromagnetic particles are in an unoxidized state.
19. The method of claim 14 , wherein the non-magnetic dielectric material matrix comprises a material selected from aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, and tantalum oxide.
20. The method of claim 14 , wherein:
the pinned layer stack comprising an antiferromagnetic pinning layer and at least one ferromagnetic pinned layer;
the pair of side shields is spaced from the first magnetic shield by a planar portion of the electrical isolation dielectric layer having a planar surface that is parallel to an interface between the first magnetic shield and the sensor layer stack; and
the second magnetic shield is formed directly on top surfaces of the pair of side shields.
21. The method of claim 20 , further comprising forming a pair of nonmagnetic spacers over the planar portion of the electrical isolation dielectric layer, wherein:
the pair of side shields is formed directly on the pair of nonmagnetic spacers; and
the pair of side shields is formed directly on a respective tapered sidewall of the electrical isolation dielectric layer.