International Business Machines Corporation

Virgil S Speriosu

Bruce Alvin Gurney

Dennis R Wilhoit

Robert Fontana

Bernard Dieny

Moris Musa Dovek

Stuart Stephen Parkin

Mohamad Towfik Krounbi

Richard Hsiao

Haralambos Lefakis

Hardayal Singh Gill

Daniele Mauri

Hugo Alberto Emilio Santini

Peter Michael Baumgart

Douglas Johnson Werner

Hugo Alberto Santini

David Eugene Heim

Ian L Sanders

Joseph Francis Smyth

Omar U Need, Iii

Tsann Lin

Ching Hwa Tsang

Kevin Robert Coffey

Daniel Rugar

William C Cain

Harry Jonathon Mamin

Steven E Lambert

Jaquelin K Spong

Serhat Metin

Kevin P Roche

Jean-Pierre Nozieres

The back end of an MR sensor and a flux guide are joined by a contiguous self-aligned junction so that a predictable overlap of the flux guide on the back end of the MR sensor can be achieved for optimizing signal flux density in the MR sensor. Lead/longitudinal bias layers for the MR sensor are also joined by a contiguous selfaligned junction to the flux guide for stabilizing the flux guide. By employing a single lift off resist mask the MR sensor and the lead/longitudinal bias layers can be patterned followed by deposition of the flux guide. The flux guide is a bilayer of an insulation material layer and a flux guide material layer. The insulation material layer is sandwiched between the MR sensor and the flux guide material layer and between the lead/longitudinal bias layers and the flux guide material layer. A heat guide or combined flux guide and heat guide may be substituted for the aforementioned flux guide.

Stabilized MR sensor and heat guide joined by contiguous junction

The back end of an MR sensor and a flux guide are joined by a contiguous self-aligned junction so that a predictable overlap of the flux guide on the back end of the MR sensor can be achieved for optimizing signal flux density in the MR sensor. Lead/longitudinal bias layers for the MR sensor are also joined by a contiguous self-aligned junction to the flux guide for stabilizing the flux guide. By employing a single lift off resist mask the MR sensor and the lead/longitudinal bias layers can be patterned followed by deposition of the flux guide. The flux guide is a bilayer of an insulation material layer and a flux guide material layer. The insulation material layer is sandwiched between the MR sensor and the flux guide material layer and between the lead/longitudinal bias layers and the flux guide material layer. A heat guide or combined flux guide and heat guide may be substituted for the aforementioned flux guide.

Stabilized MR sensor and flux/heat guide joined by contiguous junction

Stabilized MR sensor and flux guide joined by contiguous junction

Method of making stabilized MR sensor and flux guide joined by

An atomic force microscope (AFM) uses a spin valve magnetoresistive strain gauge formed on the AFM cantilever to detect deflection of the cantilever. The spin valve strain gauge operates in the absence of an applied magnetic field. The spin valve strain gauge is formed on the AFM cantilever as a plurality of films, one of which is a free ferromagnetic layer that has nonzero magnetostriction and whose magnetic moment is free to rotate in the presence of an applied magnetic field. In the presence of an applied stress to the free ferromagnetic layer due to deflection of the cantilever, an angular displacement of the magnetic moment of the free ferromagnetic layer occurs, which results in a change in the electrical resistance of the spin valve strain gauge. Electrical resistance detection circuitry coupled to the spin valve strain gauge is used to determine cantilever deflection.

Atomic force microscope system with cantilever having unbiased spin

An orthogonal spin valve read head is provided wherein a spin valve sensor is asymmetrically located between first and second shield layers so that image currents in the first and second shield layers produce a resultant image field which partially or completely counterbalances a stiffening field from antiferromagnetic, pinned and spacer layers in the MR sensor when sense current is conducted therethrough. Accordingly, the spin valve sensor may be located a greater distance from the second shield layer by providing a mid-gap layer between the spin valve sensor and a second gap layer. In one example, the total thickness of the mid-gap and second gap layer is four times as thick as the first gap layer which results in the image fields from the first and second shield layers completely counterbalancing the field from the antiferromagnetic, pinned and spacer layers due to the sense current.

Orthogonal spin valve sensor with reduced net field

A spin valve magnetoresistive (SVMR) sensor uses a laminated antiparallel (AP) pinned layer in combination with an improved antiferromagnetic (AF) exchange biasing layer. The pinned layer comprises two ferromagnetic films separated by a nonmagnetic coupling film such that the magnetizations of the two ferromagnetic films are strongly coupled together antiferromagnetically in an antiparallel orientation. This laminated AP pinned layer is magnetically rigid in the small field excitations required to rotate the SVMR sensor's free layer. When the magnetic moments of the two ferromagnetic layers in this AP pinned layer are nearly the same, the net magnetic moment of the pinned layer is small. However, the exchange field is correspondingly large because it is inversely proportional to the net magnetic moment. The laminated AP pinned layer has its magnetization fixed or pinned by an AF material that is highly corrosion resistant but that has an exchange anisotropy too low to be usable in conventional SVMR sensors. In the preferred embodiment the AF layer is nickel-oxide and is formed on one of the magnetoresistive (MR) shields that serves as the substrate. Thus the AF material also serves as the insulating MR gap material. The location of the AF layer and the laminated AP-pinned layer to which it is exchange coupled on the bottom of the SVMR sensor allows for improved longitudinal biasing of the free layer when the SVMR sensor is fabricated.

Spin valve magnetoresistive sensor with antiparallel pinned layer and

Highly sensitive orthogonal spin valve read head

Sensors based on the giant magnetoresistance effect, specifically 'spin valve' (SV) magnetoresistive sensors, have applications as external magnetic field sensors and as read heads in magnetic recording systems, such as rigid disk drives. These sensors have a ferromagnetic layer whose magnetization orientation is fixed or pinned by being exchange coupled to an antiferromagnetic layer. The magnetization of the pinned layer will become misaligned and the sensor will experience an abnormal response to the field being sensed, i.e., the external magnetic field or the recorded data in the magnetic media, if an adverse event elevates the antiferromagnetic layer above its blocking temperature. A pinned layer mangetization reset system is incorporated into systems that use SV sensors. The reset system generates an electrical current waveform that is directed through the SV sensor with an initial current value sufficient to heat the antiferromagnetic layer above its blocking temperature, and a subsequent lower current value to generate a magnetic field around the pinned layer sufficient to properly orient the magnetization of the pinned layer while the antiferromagnetic layer is cooling below its blocking temperature. This process resets the magnetization of the pinned layer to its preferred orientation and returns the SV sensor response substantially back to its desired state.

System for resetting sensor magnetization in a spin valve

A magnetoresistive (MR) sensor comprising a layered structure having at least one trilayer comprising a first and a second thin film ferromagnetic layers separated by and in interfacial contact with a third thin film non-metallic magnetic layer. A fourth thin film layer of material is within the first ferromagnetic layer, and the fourth layer has a thickness between a fraction of a monolayer and several monolayers and is located at predetermined distance from the interface between the first and third layers. A current flow is produced through the MR sensor and variations in resistivity of the MR sensor produced by rotation of the magnetization in one or both of the ferromagnetic layers is sensed as a function of the magnetic field being sensed.

Magnetoresistive sensor having multilayer thin film structure

A magnetic recording system uses an improved spin valve magnetoresistive (SVMR) sensor. The SVMR sensor has a self-pinned laminated layer as the pinned ferromagnetic layer in place of the conventional single-layer pinned layer. Because this laminated layer is 'self-pinned', a hard bias or exchange bias layer is not needed. The self-pinned laminated layer has at least two ferromagnetic films antiferromagnetically coupled to one another across a thin antiferromagnetically (AF) coupling film. Since the two ferromagnetic films in this laminated layer have their magnetic moments aligned antiparallel, their two magnetic moments can be made to essentially cancel by making the two ferromagnetic films of substantially the same thickness. The magnetic field energy generated by the signal field acting on this laminated layer will be significantly less than the effective anisotropy energy of the laminated layer. This is because the former is proportional to the difference in thicknesses of the two ferromagnetic films in the laminated layer, while the latter is proportional to the sum of the thicknesses. As a result, the laminated layer will not rotate in the presence of the signal field, but will be 'self-pinned'. The elimination of the exchange bias layer previously required for pinning also eliminates the need for Ni--Mn and its associated high-temperature process.

Spin valve magnetoresistive sensor with self-pinned laminated layer and

A magnetoresistive read sensor based on the spin valve effect in which a component of the read element resistance varies as the cosine of the angle between the magnetization directions in two adjacent magnetic layers is described. The sensor read element includes two adjacent ferromagnetic layers separated by a nonmagnetic metallic layer. A layer of antiferromagnetic material is formed over one of the ferromagnetic layers to provide an exchange bias field which fixes or 'pins' the magnetization direction in the one ferromagnetic layer. An interlayer of magnetically soft material is deposited between the ferromagnetic and antiferromagnetic layers separating the ferromagnetic layer from the antiferromagnetic layer and enhancing the exchange coupling, particularly in the instance where the ferromagnetic material is iron or an iron alloy.

Antiferromagnetic exchange coupling in magnetoresistive spin valve

A magnetic field sensor uses four individual magnetoresistive spin valve elements electrically connected in a bridge circuit. The spin valve elements are lithographically formed on the same substrate with their free layers having their magnetization axes parallel to one another. An electrically conductive fixing layer is formed on the substrate but is insulated from the spin valve elements. The application of current through the fixing conductor during fabrication of the field sensor fixes the direction of magnetization of two of the pinned layers to be antiparallel to the direction of magnetization of the other two pinned layers. The bridge circuit output voltage is responsive to an external magnetic field in the plane of the sensor. By appropriate fixing of the direction of magnetization of the pinned layers during sensor fabrication, and appropriate connection to the input and output leads, the bridge circuit output voltage is a measure of either the magnetic field or field gradient. The fixing conductor, or a separate current strap formed on the substrate, can be used to pass an unknown current over the sensor, in which case the bridge circuit output voltage is a measure of the unknown current.

Bridge circuit magnetic field sensor having spin valve magnetoresistive

A magnetoresistive read sensor based on the spin valve effect in which a component of the read element resistance varies as the cosine of the angle between the magnetization directions in two adjacent magnetic layers is described. The sensor read element includes two adjacent ferromagnetic layers separated by a nonmagnetic metallic layer. A layer of nonmagnetic electrically conductive material is deposited adjacent to and in contact with one of the ferromagnetic layers, referred to as a filter layers to form a back or conduction layer which provides a low resistance path for conduction electrons transmitted through the adjacent filter layer. The thickness of the filter layer is selected such that it effectively blocks conduction electrons having spins antiparallel to the direction of magnetization in the filter layer while allowing conduction electrons with parallel spins to be transmitted through the layer into the adjacent back layer. The magnetization of the filter layer is free to rotate in response to an applied magnetic field thereby effectively varying the electrically resistance to conduction electrons in the back/filter layer. The thickness of the back layer is selected to optimize the sensor parameters being measured and is in a range of about 4.0 A to 1000 A.

Magnetoresistive spin valve sensor having a nonmagnetic back layer

A magnetic recording data storage system of high recording density is made possible by an improved magnetoresistive sensor. The sensor has a ferromagnetic sensing layer that is a laminated layer of two ferromagnetic films antiferromagnetically coupled to one another and separated by an antiferromagnetically coupling film. By appropriate selection of the thickness of the nonmagnetic antiferromagnetically coupling film, the ferromagnetic films become antiferromagnetically coupled and their magnetizations rotate as a single rigid unit in the presence of the external magnetic field to be sensed. The ferromagnetic sensing layer can be used in conventional magnetoresistive sensors of the anisotropic magnetoresistive (AMR) type and in spin valve magnetoresistive (SVMR) sensors. In the spin valve sensor, the laminated ferromagnetic sensing layer serves as the free layer and is preferably formed of two films of nickel-iron (Ni-Fe) separated by a ruthenium (Ru) antiferromagnetically coupling film. Because the two ferromagnetic films have their moments aligned antiparallel, then, assuming the two films are made of the same material, by selecting the two films to have different thicknesses the effective free layer thickness can be reduced without significantly reducing the magnetoresistance.

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Virgil S Speriosu