Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-09-19
2003-11-25
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S319000
Reexamination Certificate
active
06654209
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to magnetic recording heads, and more particularly, to a lead structure for a read head of such recording heads.
BACKGROUND OF THE INVENTION
Devices utilizing the giant magnetoresistance (GMR) effect have utility as magnetic sensors, especially as read sensors in read heads used in magnetic disc storage systems. The GMR effect is observed in thin, electrically conductive multi-layer systems having magnetic layers. A type of magnetic sensor utilizing the GMR effect is referred to as a “spin valve” sensor.
A spin valve sensor may include a sandwiched structure having two ferromagnetic layers separated by a thin non-ferromagnetic layer. One of the ferromagnetic layers is called the “pinned layer” because it is magnetically pinned or oriented in a fixed and unchanging direction. A common method of maintaining the magnetic orientation of the pinned layer is through exchange coupling utilizing a proximate, i.e. adjacent or nearby, anti-ferromagnetic layer, commonly referred to as the “pinning layer.” The other ferromagnetic layer is called the “free” or “unpinned” layer because its magnetization can rotate in response to the presence of external magnetic fields.
The benefits of spin valve sensors result from a large difference in electrical conductivity exhibited by the devices depending on the relative alignment between the magnetizations of the GMR element ferromagnetic layers. In order for antiferromagnetically pinned spin valve sensors to function effectively, a sufficient pinning field from the pinning layer is required to keep the pinned ferromagnetic layer's magnetization unchanged during operation. Various anti-ferromagnetic materials, such as PtMn, NiMn, FeMn, NiO, IrMn, PtPdMn, CrMnPt, RuRhMn, and TbCo, have been used or proposed as antiferromagnetic pinning layers for spin valve sensors. GMR sensors can be used to sense information encoded in magnetic storage media. In operation, a sense current is passed through a read head of the magnetic disc storage system. The presence of a magnetic field in the storage media adjacent to the sensor changes the resistance of the sensor. A resulting change in voltage drop across the sensor due to the change of the resistance of the sensor can be measured and used to recover magnetically stored information.
These sensors typically comprise a stack of thin sheets of a ferromagnetic alloy, such as NiFe (Permalloy), magnetized along an axis of low coercivity. The sheets may be mounted in the read head so that, for example, the magnetic axes are transverse to the direction of disc rotation for the pinned layer and parallel to the plane of the disc for the free layer. The magnetic flux from the disc causes rotation of the magnetization vector in at least one of the sheets, which in turn causes a change in resistivity of the sensor.
A read head for use in a disc drive can include a first shield, a second shield, and a GMR sensor, or also referred to as a GMR stack, located between the first shield and the second shield. For operation of the sensor, a sense current is caused to flow through the read head and particularly through the sensor. As resistance of the sensor changes, the voltage across the sensor changes. This is used to produce an output voltage.
The output voltage is affected by various characteristics of the sensor. The sense current can flow through the sensor in a direction that is perpendicular to the planes of the layers or stack strips that comprise the sensor, i.e. current-perpendicular-to-plane component or CPP, or the sense current can flow through the sensor in a direction that is parallel to the planes of the layers or stack strips, i.e. current-in-plane or CIP. The CPP operating mode can result in higher output voltage than the CIP operating mode. The higher the output voltage, the greater the precision and sensitivity of the read head sensor in sensing magnetic fields from the magnetic medium. Therefore, it is desirable to maximize the output voltage of the read head and specifically the sensor thereof.
Current perpendicular to the plane GMR sensors are known to have a relatively low resistance. There have been three primary approaches to overcoming the problem of low sensor resistance of CPP giant magnetoresistance (GMR) sensors and allowing the GMR to be measured. One approach uses superconducting contacts and measures the GMR at low temperatures. A second approach involves making the sensor or GMR stack very thick to raise its resistance. A third approach involves making a very small sensor or GMR stack to increase its resistance. The first two approaches are not practical when it comes to the making of the CPP-GMR sensor for use in a magnetic recording head. The disc drive cannot run at very low temperatures nor can the sensor be more than 100's of nanometers thick. The two main problems with the third approach relate to manufacturing the small devices and achieving a low contact resistance. The contact resistance is significant for small devices since the contact resistance varies as the inverse of the sensor area.
In addition to the importance of having a low contact resistance between the lead and the sensor, it is also important to have a low lead resistance leading up to this contact. Specifically, a relatively high lead resistance will decrease the overall GMR effect making the GMR more difficult to measure.
There is a need for an improved low resistance lead structure for a magnetic recording head.
SUMMARY OF THE INVENTION
The invention meets the identified need, as well as other needs, as will be more fully understood following a review of this specification and drawings.
In accordance with an aspect of the invention, a current perpendicular to the plane read head comprises a read sensor and a lead structure positioned adjacent to read sensor. The lead structure includes a layer of conductive material that forms at least a portion thereof, wherein the layer of conductive material has a lower resistivity than a resistivity of the remainder of the lead structure. The layer of conductive material with lower resistivity decreases the overall resistance of the lead structure. By reducing the overall lead structure resistance, the read sensor is allowed to more efficiently perform its intended function. In order to decrease the overall resistance of the lead structure, the layer of conductive material may be deposited on the lead structure either proximate to the read sensor or positioned for contact with the read sensor.
In accordance with another aspect of the invention, a current perpendicular to the plane read head comprises a read sensor and a lead structure positioned adjacent the read sensor. The lead structure includes means for reducing the resistivity of the lead structure.
In accordance with yet another aspect of the invention, a read head for a magnetic disc storage system comprises first and second lead structures and a current perpendicular to the plane read sensor between the first and second lead structures. Each of the first and second lead structures include a layer of conductive material that forms at least a portion thereof. The layers of conductive material have a lower resistivity than a resistivity of the remainder of the first and second lead structures.
In accordance with a further aspect of the invention, a read head for a magnetic disc storage system comprises first and second lead structures and a current perpendicular to the plane read sensor between the first and second lead structures. At least one of the first and second lead structures includes means for reducing the resistivity of the first and second lead structures.
In accordance with another aspect of the invention, a magnetic disc drive storage system comprises a housing, a rotatable magnetic storage medium positioned in the housing and a movable recording head mounted in the housing adjacent the magnetic storage medium. The recording head includes a current perpendicular to the plane read head. The current perpendicular to the plane read head comprises first and second
Crue Billy Wayne
Parker Gregory John
Seigler Michael Allen
Van der Heijden Petrus Antonius
Evans Jefferson
Pietragallo Bosick & Gordon
Queen, II Benjamin T.
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