Abstract: An exchange-coupled magnetic structure includes a ferromagnetic layer, a coercive ferrite layer, such as cobalt-ferrite, for biasing the magnetization of the ferromagnetic layer, and an oxide underlayer, such as cobalt-oxide, in proximity to the coercive ferrite layer. The oxide underlayer has a lattice structure of either rock salt or a spinel and exhibits no magnetic moment at room temperature. The underlayer affects the structure of the coercive ferrite layer and therefore its magnetic properties, providing increased coercivity and enhanced thermal stability. As a result, the coercive ferrite layer is thermally stable at much smaller thicknesses than without the underlayer. The exchange-coupled structure is used in spin valve and magnetic tunnel junction magnetoresistive sensors in read heads of magnetic disk drive systems. Because the coercive ferrite layer can be made as thin as 1 nm while remaining thermally stable, the sensor satisfies the narrow gap requirements of high recording density systems.

Abstract: The current invention provides for magnetic sensor devices with reduced gap thickness and improved thermal conductivity. Gap structures of the current invention are integrated in laminated Magneto-Resistive and Spin-Valve sensors used in magnetic data storage systems. The gap structures are produced by depositing metal layers and oxidizing portions of or all of the metal layers to form thin high quality oxidized metal dielectric separator layers. The oxidized metal layer provides for excellent electrical insulation of the sensor element and any remaining metallic portions of the metal layers provide a thermally conducting pathway to assist the dissipation of heat generated by the sensor element. Because of the combined qualities of electrical insulation and thermal conductivity, magnetic sensor devices of this invention can be made with thinner gap structures and operated at higher drive currents.

Abstract: A CPP magnetoresistive sensor with a spacer layer made of a heterogeneous material, which is composed of conductive grains within a highly resistive matrix, has a high resistance. The conductive grains are typically made of a conductive element or alloy that can operate as a GMR spacer material. The highly resistive matrix is typically made of a highly resistive or insulating element, alloy or compound that will hinder the flow of electrons. The sensing electrical current is passed through the conductive grains, which are typically made of the same material as GMR spacers, so the GMR is maintained even though the overall resistance is increased.

Abstract: An exchange-coupled magnetic structure of a cobalt-ferrite layer adjacent a magnetic metal layer is used in magnetorestive sensors, such as spin valves or tunnel junction valves. The exchange-coupled magnetic structure is used in a pinning structure pinning the magnetization of a ferromagnetic pinned layer, or in an AP pinned layer. A low coercivity ferrite may be used in an AP free layer. Cobalt-ferrite layers may be formed by co-sputtering of Co and Fe in an oxygen/argon gas mixture, or by sputtering of a CoFe2 composition target in an oxygen/argon gas mixture. Alternatively, the cobalt-ferrite layer may be formed by evaporation of Co and Fe from an alloy source or separate sources along with a flux of oxygen atoms from a RF oxygen atom beam source. Magnetoresistive sensors including cobalt-ferrite layers have small read gaps and produce large signals with high efficiency.

Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films antiferromagnetically coupled together across a nonferromagnetic spacer film. The magnetic moments of the two antiferromagnetically-coupled films are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of the recording layer is the difference in the Mrt values of the two ferromagnetic films. This reduction in Mrt is accomplished without a reduction in the thermal stability of the recording medium because the volumes of the grains in the antiferromagnetically-coupled films add constructively. In a magnetic recording rigid disk application, the magnetic layer comprises two ferromagnetic films, each a granular film of a sputter deposited CoPtCrB alloy, separated by a Ru spacer film having a thickness to maximize the antiferromagnetic exchange coupling between the two CoPtCrB films.

Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films antiferromagnetically coupled together across a nonferromagnetic spacer film. The magnetic moments of the two antiferromagnetically-coupled films are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of the recording layer is the difference in the Mrt values of the two ferromagnetic films. This reduction in Mrt is accomplished without a reduction in the thermal stability of the recording medium because the volumes of the grains in the antiferromagnetically-coupled films add constructively. In a magnetic recording rigid disk application, the magnetic layer comprises two ferromagnetic films, each a granular film of a sputter deposited CoPtCrB alloy, separated by a Ru spacer film having a thickness to maximize the antiferromagnetic exchange coupling between the two CoPtCrB films.

Abstract: A longitudinal bias structure to be placed adjacent a ferromagnetic free layer or a sense layer which is responsive to an external magnetic field and belongs to a magnetic sensor, for example a magnetic readback sensor such as an anisotropic magnetoresistive (AMR) sensor, giant magnetoresistive (GMR) sensor such as GMR spin valve sensor or GMR multilayer sensor or in tunnel valve sensor. The longitudinal bias structure is built up of a top ferromagnetic bias layer of first thickness t1 having a first magnetic moment M1, a bottom ferromagnetic bias layer of second thickness t2 having a second magnetic moment M2 which is anti-parallel to first magnetic moment M1 of the top ferromagnetic bias layer, and an exchange-coupling layer disposed between the top and bottom bias layers.

Abstract: 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.

Abstract: 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.

Abstract: 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.