Abstract: An antiferromagnetically exchange-coupled structure for use in various types of magnetic devices, such as magnetic tunnel junctions and spin-valve giant magnetoresistance recording heads, includes an antiferromagnetic layer formed of an alloy of osmium and manganese, wherein the osmium is present in the range of approximately 10 to 30 atomic %. The antiferromagnetic layer is deposited on a non-reactive underlayer, preferably one formed of a noble metal, such as platinum, palladium or alloys thereof. The antiferromagnetic material provides a strong exchange biasing for the ferromagnetic layer that is deposited on the antiferromagnetic layer. Iridium may be added to the osmium-manganese alloy, wherein the total of osmium and iridium is in the range of the approximately 10 to 30 atomic %, to increase the blocking temperature of the antiferromagnetic material.

Abstract: A non-volatile memory array includes a plurality of memory cells. Each memory cell includes a magnetic tunnel junction device having a first free ferromagnetic layer, a second free ferromagnetic layer and a highly conductive layer. The first ferromagnetic layer of each magnetic tunnel junction device extends in a direction that is substantially parallel to the second ferromagnetic layer of the magnetic tunnel junction device. The highly conductive layer of each magnetic tunnel junction device is formed between the first ferromagnetic layer and the second ferromagnetic layer of the magnetic tunnel junction device. A write current through each selected memory cell flows into the highly conductive layer and along at least a portion of the highly conductive layer. A self-field associated with the write current changes a first predetermined magnetization of the first and second ferromagnetic layers to a second predetermined magnetization.

Abstract: A magnetic tunnel junction (MTJ) device has sufficiently small area to make it commercially practical as both a magnetic memory cell and a magnetoresistive read head. The small area magnetic tunnel junction device has both low resistance and high magnetoresistance. The magnetic tunnel junction device is made possible by the use of a thin aluminum layer in a thickness range of approximately 5-12 Angstroms. The Al layer is completely oxidized, without oxidizing the adjacent ferromagnetic layers, to form the insulating tunnel barrier layer of the MTJ.

Abstract: Non-magnetic transition metal spacer layers 2.5 to 50 Angstroms thick with compositions of Os, Ru and Re are used in laminated magnetic structures. The ultra-thin non-magnetic transition metal spacer layers are useful to fabricate micron and sub-micron laminated magnetic devices. The laminated magnetic structures using ultra-thin non-magnetic transition metal spacer layers of Os, Ru and Re have anti-ferromagnetic coupling between the magnetic layers. The anti-ferromagnetic coupling provides a mechanism for reduced edge curling and efficient directional magnetization. Alloying the non-magnetic transition metal layer provides a method for engineering coupling strengths, coercivities and remanences in magnetic structures useful for high frequency applications. These laminated magnetic structure have applications in magnetic read head, magnetic write head, magnetic memory, and miniature transformer devices.

Abstract: An improved magnetic tunnel junction (MTJ) memory cell for use in a nonvolatile magnetic random access memory (MRAM) array has a free layer formed as two ferromagnetic films that are magnetostatically coupled antiparallel to one another by their respective dipole fields. The magnetostatic or dipolar coupling of the two ferromagnetic films occurs across a nonferromagnetic spacer layer that is selected to prevent exchange coupling between the two ferromagnetic films. The magnetic moments of the two ferromagnetic films are antiparallel to another so that the multilayer free layer structure has a reduced net magnetic moment.

Abstract: A magnetic device uses laminated ferromagnetic layers containing antiferromagnetically coupled ferromagnetic films coupled together with improved antiferromagnetically coupling (AFC) films. The AFC films are formed of the binary and ternary alloys comprising combinations of Ru, Os and Re. The ferromagnetic film thicknesses, the AFC film thicknesses and the compositions of the films in the laminated layer can be varied to engineer the magnetic properties of the device. The magnetic devices whose properties are improved with the improved laminated layers include spin valve magnetoresistive read heads and magnetic tunnel junction (MTJ) devices for use as magnetic memory cells and magnetoresistive read heads.

Abstract: A magnetic tunnel junction (MTJ) memory cell uses a biasing ferromagnetic layer in the MTJ stack of layers that is magnetostatically coupled with the free ferromagnetic layer in the MTJ stack to provide transverse and/or longitudinal bias fields to the free ferromagnetic layer. The MTJ is formed on an electrical lead on a substrate and is made up of a stack of layers.

Abstract: A magnetoresistive sensor for use as the read sensor in magnetic recording disk drives uses a permalloy (approximate composition of Ni.sub.81,Fe.sub.19) sensor layer with a magnetoresistance coefficient significantly greater than prior art permalloy sensor layers for a range of permalloy film thicknesses. The permalloy film is deposited on a substrate, such as alumina, that is essentially non-reactive with permalloy at elevated temperatures while the substrate is heated. The permalloy films have a zero or slightly negative magnetostriction, low easy and hard axis coercivities, and a low anisotropy field. At very small film thicknesses the permalloy films formed with substrate heating exhibit an even greater percentage increase in magnetoresistance coefficient than at higher film thicknesses, thereby allowing the films to function in magnetic recording disk drive heads for use at very high linear recording densities.

Abstract: A magnetic tunnel junction (MTJ) magnetoresistive (MR) read head has one fixed ferromagnetic layer and one sensing ferromagnetic layer on opposite sides of the tunnel barrier layer, and with a biasing ferromagnetic layer in the MTJ stack of layers that is magnetostatically coupled with the sensing ferromagnetic layer to provide either longitudinal bias or transverse bias or a combination of longitudinal and transverse bias fields to the sensing ferromagnetic layer. The magnetic tunnel junction in the MTJ MR head is formed on an electrical lead on a substrate and is made up of a stack of layers.

Abstract: A magnetic tunnel junction magnetoresistive read head has one fixed ferromagnetic layer and one generally rectangularly shaped sensing ferromagnetic layer on opposite sides of the tunnel barrier layer, and a biasing ferromagnetic layer located around the side edges and back edges of the sensing ferromagnetic layer. An electrically insulating layer separates the biasing layer from the edges of the sensing layer. The biasing layer is a continuous boundary biasing layer that has side regions and a back region to surround the three edges of the sensing layer. When the biasing layer is a single layer with contiguous side and back regions its magnetic moment can be selected to make an angle with the long edges of the sensing layer. In this manner the biasing layer provides both a transverse bias field to compensate for transverse ferromagnetic coupling and magnetostatic coupling fields acting on the sensing layer to thus provide for a linear response of the head and a longitudinal bias field to stabilize the head.

Abstract: An improved magnetic tunnel junction (MTJ) device for use in a magnetic recording read head or in a magnetic memory storage cell is comprised of two ferromagnetic layers, a "hard" or "fixed" ferromagnetic layer and a sensing or "free" ferromagnetic layer, which are separated by a thin insulating tunneling layer. Each of the ferromagnetic layers is a multilayer formed from two thinner ferromagnetic films coupled antiferromagnetically to one another across a thin antiferromagnetically coupling film. The antiferromagnetically coupling film is chosen, with regard to material composition and thickness, so that it causes the two ferromagnetic films which sandwich it to have their magnetic moments arranged antiparallel to one other in the absence of external magnetic fields. The magnetic moments of the fixed ferromagnetic multilayer and free ferromagnetic layer can be chosen to be arbitrarily small by making the two ferromagnetic films comprising each of them to have substantially the same magnetic moment.

Abstract: A magnetic tunnel junction (MTJ) of the type using soft (low magnetic coercivity) and hard (high magnetic coercivity) ferromagnetic layers separated by an insulating tunnel barrier (a hard/soft MTJ device) is stable without loss of magnetization after repeated cycling of its magnetic state. The MTJ device is based on the discovery that the mechanism of demagnetization in a hard/soft MTJ device is via coupling of the hard ferromagnetic layer to the soft ferromagnetic layer via the formation and motion of domain walls in the soft ferromagnetic layer. The MTJ device includes adjacent ferromagnetic structures that provide a transverse biasing magnetic field to the soft ferromagnetic layer. The transverse biasing field permits coherent rotation of the magnetic moment of the soft ferromagnetic layer without the formation of magnetic domains when suitable switching fields are applied.

Abstract: A magnetic tunnel junction (MTJ) magnetoresistive read head for a magnetic recording system has the MTJ sensing or free ferromagnetic layer also functioning as a flux guide to direct magnetic flux from the magnetic recording medium to the tunnel junction. The MTJ fixed ferromagnetic layer and the MTJ tunnel barrier layer have their front edges substantially coplanar with the sensing surface of the head. Both the fixed and free ferromagnetic layers are in contact with opposite surfaces of the MTJ tunnel barrier layer but the free ferromagnetic layer extends beyond the back edge of either the tunnel barrier layer or the fixed ferromagnetic layer, whichever back edge is closer to the sensing surface. This assures that the magnetic flux is non-zero in the tunnel junction region.

Abstract: A magnetic tunnel junction (MTJ) magnetoresistive read head for a magnetic recording system has the MTJ sensing or free ferromagnetic layer also functioning as a flux guide to direct magnetic flux from the magnetic recording medium to the tunnel junction. The MTJ fixed ferromagnetic layer has its front edge recessed from the sensing surface of the head. Both the fixed and free ferromagnetic layers are in contact with opposite surfaces of the MTJ tunnel barrier layer but the free ferromagnetic layer extends beyond the back edge of either the tunnel barrier layer or the fixed ferromagnetic layer, whichever back edge is closer to the sensing surface. This assures that the magnetic flux is non-zero in the tunnel junction region. The magnetization direction of the fixed ferromagnetic layer is fixed in a direction generally perpendicular to the sensing surface and thus to the magnetic recording medium, preferably by interfacial exchange coupling with an antiferromagnetic layer.

Abstract: A magnetic tunnel junction (MTJ) magnetoresistive read head for a magnetic recording system has the MTJ device located between two spaced-apart magnetic shields. The magnetic shields, which allow the head to detect individual magnetic transitions from the magnetic recording medium without interference from neighboring transitions, also function as electrical leads for connection of the head to sense circuitry. Electrically conductive spacer layers are located at the top and bottom of the MTJ device and connect the MTJ device to the shields. The thickness of the spacer layers is selected to optimize the spacing between the shields, which is a parameter that controls the linear resolution of the data that can be read from the magnetic recording medium.

Abstract: A magnetic tunnel junction (MTJ) device is usable as a magnetic field sensor or as a memory cell in a magnetic random access (MRAM) array. The MTJ device has a "pinned" ferromagnetic layer whose magnetization is oriented in the plane of the layer but is fixed so as to not be able to rotate in the presence of an applied magnetic field in the range of interest, a "free" ferromagnetic layer whose magnetization is able to be rotated in the plane of the layer relative to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier layer located between and in contact with both ferromagnetic layers. The pinned ferromagnetic layer is formed as a sandwich of two antiferromagnetically coupled ferromagnetic layers separated by a metallic layer. The free and pinned ferromagnetic layers are located in separate spaced-apart planes so as to not overlap the tunnel barrier layer.

Abstract: A magnetic tunnel junction device usable as a memory cell or an external magnetic field sensor uses a multilayer of ferromagnetic layers in place of a single hard high-coercivity ferromagnetic layer in one of the two magnetic tunnel junction electrodes. The magnetic tunnel junction element in the device is made up of a ferromagnetic multilayer structure that has high coercivity to maintain its magnetic moment fixed in the presence of an applied magnetic field in the range of interest, a single free ferromagnetic layer whose magnetic moment is free to rotate, and an insulating tunnel barrier layer located between and in contact with the ferromagnetic multilayer structure and the free ferromagnetic layer.

Abstract: A magnetic tunnel junction device, usable as a memory cell or an external magnetic field sensor, has a tunneling magnetoresistance response, as a function of applied magnetic field, that is substantially symmetric about zero field. The magnetic tunnel junction is made up of two ferromagnetic layers, one of which has its magnetic moment fixed and the other of which has its magnetic moment free to rotate, an insulating tunnel barrier layer between the ferromagnetic layers for permitting tunneling current perpendicularly through the layers, and a nonferromagnetic layer located at the interface between the tunnel barrier layer and one of the ferromagnetic layers. The nonferromagnetic layer increases the spacing between the tunnel barrier layer and the ferromagnetic layer at the interface and thus reduces the magnetic coupling between the fixed and free ferromagnetic layers, which has been determined to be the cause of unsymmetric tunneling magnetoresistance response about zero field.

Abstract: A magnetic tunnel junction device for use as a magnetic memory cell or a magnetic field sensor has one fixed ferromagnetic layer and one sensing ferromagnetic layer formed on opposite sides of the insulating tunnel barrier layer, and a hard biasing ferromagnetic layer that is electrically insulated from but yet magnetostatically coupled with the sensing ferromagnetic layer. The magnetic tunnel junction in the device is formed on an electrical lead on a substrate and is made up of a stack of layers. The layers in the stack are an antiferromagnetic layer, a fixed ferromagnetic layer exchange biased with the antfferromagnetic layer so that its magnetic moment cannot rotate in the presence of an applied magnetic field, an insulating tunnel barrier layer in contact with the fixed ferromagnetic layer, and a sensing ferromagnetic layer in contact with the tunnel barrier layer and whose magnetic moment is free to rotate in the presence of an applied magnetic field.

Abstract: A magnetic tunnel junction (MTJ) device is usable as a magnetic field sensor or as a memory cell in a magnetic random access (MRAM) array. The MTJ device has a "pinned" ferromagnetic layer whose magnetization is oriented in the plane of the layer but is fixed so as to not be able to rotate in the presence of an applied magnetic field in the range of interest, a "free" ferromagnetic layer whose magnetization is able to be rotated in the plane of the layer relative to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier layer located between and in contact with both ferromagnetic layers. The pinned ferromagnetic layer is pinned by interfacial exchange coupling with an adjacent antiferromagnetic layer. The amount of tunneling current that flows perpendicularly through the two ferromagnetic layers and the intermediate tunnel barrier layer depends on the relative magnetization directions of the two ferromagnetic layers.