Leland Stanford Junior University

Censtor Corporation

United States of America As Represented by the Administrator of Nasa

Densitek Corporation

Bruce M Lairson

Mark R Visokay

Jonathan Zanhong Sun

Theodore H Geballe

Bruce M Clemens

John D Olivas

Robert Sinclair

Rajeshuni Ramesham

Wenhong Liu

An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure, which may be a cantilever, membrane, bridge, or other microelement, moves under the influence of an acceleration a known displacement predicted by the configuration and materials selected, and the resulting change in the electrical resistance of the MR sensor can be used to calculate the displacement. Using a micromachining approach, very thin silicon and silicon nitride membranes are fabricated in one preferred embodiment by means of anisotropic etching of silicon wafers. Other approaches include reactive ion etching of silicon on insulator (SOI), or Low Pressure Chemical Vapor Deposition of silicon nitride films over silicon substrates. The device is found to be improved with the use of giant magnetoresistive elements to detect changes in the local magnetic field.

Ultra-sensitive magnetoresistive displacement sensing device

A hard disk drive has a head with a read element adjacent to a write element, with the write element extending closer to the disk than the read element so that the write element is proximate to the disk for writing sharp patterns and the read element is removed from the disk to avoid wear and thermal asperities. The write element is encompassed with diamond-like carbon (DLC) to allow at least occasional dynamic contact with the disk while the read element, which includes a magnetoresistive material, is disposed in a recessed area and may be covered with a thin coating of DLC to avert corrosion. The disk may have a multilayer granular media for low-noise, high-strength perpendicular data storage. Perpendicular data storage may also be provided by keeping the write element in such close proximity to the media that perpendicular write fields predominate, while perpendicular signals from the media are favored by the read element.

Hard disk drive having contact write and recessed magnetoresistive read

A new type of multilayer structure is shown which has superior properties for retaining magnetic transitions on a surface as they are written by a recording transducer. The multilayer is composed of crystal grains which are electronically isolated from one another (exchange isolated). The exchange isolation of the grains creates a type of medium which can viably store data at more than 2 billions bits per square inch. A method is described for making such a structure and the storage of magnetic transitions at extremely high density is demonstrated. Recording with previous multilayer candidates is also shown for comparison purposes.

Grain isolated multilayer perpendicular recording medium

A hard disk drive has a head with a read element adjacent to a write element, with the write element extending closer to the disk than the read element so that the write element is close to the disk for writing sharp patterns and the read element is removed from the disk to avoid wear and thermal asperities. The write element is encompassed with diamond-like carbon (DLC) to allow at least occasional dynamic contact with the disk while the read element, which includes a magneto resistive material, is disposed in a recessed area and may be covered with a thin coating of DLC to avert corrosion. The disk may have a multilayer granular media for low-noise, high-strength perpendicular data storage. Perpendicular data storage may also be provided by keeping the write element in such close proximity to the media that perpendicular write fields predominate, while perpendicular signals from the media are favored by the read element.

Hard disk drive having contact write and recessed magnetorestive read

A method for making oriented thin films of a ternary intermetallic compound and such films having a tetragonal structure and generally uniaxial magnetic, optical, electronic, and mechanical properties, as well as a generally lower Curie temperature than oriented binary intermetallic films. The steps of the method involve selecting a substrate material for biasing the orientation of the ternary intermetallic compound and exhibiting no chemical reactiveness to the ternary intermetallic compound. Preferably, such substrate is a single crystal, such as MgO or Al.sub.2 O.sub.3, or an amorphous material such as pure SiO.sub.2, amorphous carbon, or glass. In a second step the substrate is heated to a temperature above 450.degree. C. and then, a first metal, a second metal, and a third metal are simultaneously deposited on the substrate material. The first metal and second metal are selected from among metals pairs including CoNi, CoFe, FeNi, and the third metal is selected from the group of metals consisting of Pd and Pt. The thin film formed is a ternary intermetallic compound exhibiting an L1.sub.0 crystal structure and the desired uniaxial properties. The method of the invention allows one to accurately control the relative amounts of the three metals.

Method for producing uniaxial tetragonal thin films of ternary

A method for producing oriented, intermetallic, thin film structures having uniaxial magnetic, electronic, optical, and mechanical properties. Artificial superlattices (10) are assembled by sputter deposition of alternating layers of the component metals of the target intermetallic compound on an aligned substrate (16). Either single crystal substrates or crystallographically textured substrates may be used to induce alignment of the deposited layers (10, 12) in the method of the present invention. Annealing of the resulting superlattice (10) generates aligned, thin film intermetallic compounds (38) of the component metals at the interfaces (44) of the superlattice (10), the thin film intermetallic compounds having pronounced, uniaxial properties.

Uniaxial thin film structures formed from oriented bilayers and

Magnetic shielding currents having a critical current density, Jc, at a superconducting temperature are stabilized by reducing the temperature of the superconducting body after a steady state or persistent current is established. The current density of the current at the reduced temperature is below the critical current density for the material at the reduced temperature. Decay of the magnetic shielding current at the reduced temperature is significantly reduced.

Growing community of inventors

Houston, TX, United States of America

Bruce M Lairson