US 6,185,079 B2 · Disk drive with thermal asperity reduction circuitry using a magnetic tunnel junction sensor

Abstract

A disk drive system having a magnetic tunnel junction (MTJ) sensor having two MTJ stacks between first and second shields and a common electrode disposed between the two MTJ stacks. A first sense current is provided to the first MTJ stack by the first shield and the common electrode and a second sense current is provided to the second MTJ stack by the second shield and the common electrode. The magnetization directions of the pinned layers of the first and second MTJ stacks are fixed perpendicular to the ABS and antiparallel with respect to each other so that the magnetoresistive signal generated due to an external field from a disk by the first MTJ stack differs in phase by 180° with respect to the magnetoresistive signal generated due to the same external field by the second MTJ stack. The voltages developed across the two MTJ stacks (voltages due to the presence of thermal asperities and voltages due to the presence of data fields) are applied to the inputs of a differential amplifier for substantial elimination of the thermal asperity signal.

Claims37

Dependent claims

A magnetic tunnel junction (MTJ) sensor, comprising:

a first MTJ (MTJ1) stack, said MTJ1 stack having:
a ferromagnetic free layer;
a ferromagnetic pinned layer;
a tunnel barrier layer disposed between said free layer and said pinned layer;
and
an antiferromagnetic (AFM1) layer in contact with said ferromagnetic pinned layer for pinning the magnetization of said pinned layer;
a second MTJ (MTJ2) stack, said MTJ2 stack having:
a ferromagnetic free layer;
a ferromagnetic pinned layer;
a tunnel barrier layer disposed between said free layer and said pinned layer;
and
an antiferromagnetic (AFM2) layer in contact with said ferromagnetic pinned layer for pinning the magnetization of said pinned layer;
a common electrode disposed between said MTJ1 stack and said MTJ2 stack;
a first shield (S1) in contact with said MTJ1 stack for providing a first sense current to said MTJ1 stack;
and
a second shield (S2) in contact with said MTJ2 stack for providing a second sense current to said MTJ2 stack.

13 more elements

A disk drive system comprising:

a magnetic recording disk;
a magnetic tunnel junction (MTJ) sensor for sensing magnetically recorded data on said magnetic recording disk, said MTJ sensor comprising:
a first MTJ (MTJ1) stack, said MTJ1 stack having:
a ferromagnetic free layer;
a ferromagnetic pinned layer;
a tunnel barrier layer disposed between said free layer and said pinned layer;
and
an antiferromagnetic (AFM1) layer in contact with said ferromagnetic pinned layer for pinning the magnetization of said pinned layer;
a second MTJ (MTJ2) stack, said MTJ2 stack having:
a ferromagnetic free layer;
a ferromagnetic pinned layer;
a tunnel barrier layer disposed between said free layer and said pinned layer;
and
an antiferromagnetic (AFM2) layer in contact with said ferromagnetic pinned layer for pinning the magnetization of said pinned layer;
a common electrode disposed between said MTJl stack and said MTJ2 stack;
a first shield (S1) in contact with said MTJl stack for providing a first sense current to said MTJ1 stack;
and
a second shield (S2) in contact with said MTJ2 stack for providing a second sense current to said MTJ2 stack;
an actuator for moving said MTJ sensor across the magnetic recording disk so the MTJ sensor may access different regions of magnetically recorded data on the magnetic recording disk;
and
a recording channel coupled electrically to the MTJ sensor for detecting changes in resistance of the MTJ sensor caused by rotation of the magnetization axis of the free ferromagnetic layers relative to the fixed magnetization of the pinned layers in response to magnetic fields from the magnetically recorded data.

18 more elements

A disk drive system comprising:

a magnetic recording disk;
a magnetic tunnel junction (MTJ) sensor for sensing magnetically recorded data on said magnetic recording disk, said MTJ sensor comprising:
a first MTJ (MTJ1) stack, said MTJ1 stack having:
a ferromagnetic free layer;
a laminated antiparallel (AP) pinned layer, said AP-pinned layer comprising a first ferromagnetic sublayer (FM1), a second ferromagnetic sublayer (FM2), and an antiparallel coupling (APC) layer disposed between said FM1 sublayer and said FM2 sublayer;
a tunnel barrier layer disposed between said free layer and said FM1 sublayer;
and
an antiferromagnetic (AFML) layer in contact with said FM2 sublayer for pinning the magnetization of said FM2 sublayer;
a second MTJ (MTJ2) stack, said MTJ2 stack having:
a ferromagnetic free layer;
a ferromagnetic pinned layer;
a tunnel barrier layer disposed between said free layer and said pinned layer;
and
an antiferromagnetic (AFM2) layer in contact with said ferromagnetic pinned layer for pinning the magnetization of said pinned layer;
a common electrode disposed between said MTJ1 stack and said MTJ2 stack;
a first shield (S1) in contact with said MTJ1 stack for providing a first sense current to said MTJ1 stack;
and
a second shield (S2) in contact with said MTJ2 stack for providing a second sense current to said MTJ2 stack;
an actuator for moving said MTJ sensor across the magnetic recording disk so the MTJ sensor may access different regions of magnetically recorded data on the magnetic recording disk;
and
a recording channel coupled electrically to the MTJ sensor for detecting changes in resistance of the MTJ sensor caused by rotation of the magnetization axis of the free ferromagnetic layers relative to the fixed magnetization of the pinned layers in response to magnetic fields from the magnetically recorded data.

18 more elements

Dependencies are inferred from the claim text.

Disk drive with thermal asperity reduction circuitry using a magnetic tunnel junction sensor

Life of this patent

Disk drive with thermal asperity reduction circuitry using a magnetic tunnel junction sensor

Life of this patent

Abstract

Claims37