PubMed Health⌕ Search

Biomedical subjects

R A Buhrman

Publications and source records attributed to R A Buhrman.

6 recordsLinked to original sources
PubMed2002

Quantitative study of magnetization reversal by spin-polarized current in magnetic multilayer nanopillars.

We have studied magnetic switching by spin-polarized currents and also the magnetoresistance in sub-100-nm-diam thin-film Co/Cu/Co nanostructures, with the current flowing perpendicular to the plane of the films. By independently varying the thickness of all three layers and measuring the change of the switching currents, we test the theoretical models for spin-transfer switching. In addition, the changes in the switching current and magnetoresistance as a function of the Cu layer thickness give two independent measurements of the room-temperature spin-diffusion length in Cu.

Journal Article↗
PubMed2002

Thermally activated magnetic reversal induced by a spin-polarized current.

We have measured the statistical properties of magnetic reversal in nanomagnets driven by a spin-polarized current. Like reversal induced by a magnetic field, spin-transfer-driven reversal near room temperature exhibits the properties of thermally activated escape over an effective barrier. However, the spin-transfer effect produces qualitatively different behaviors than an applied magnetic field. We discuss an effective current vs field stability diagram. If the current and field are tuned so that their effects oppose one another, the magnet can exhibit telegraph-noise switching.

Journal Article↗
PubMed2002

Ultrathin aluminum oxide tunnel barriers.

Ballistic electron emission microscopy is used to study the formation of ultrathin tunnel barriers by the oxidization of aluminum. An O2 exposure, approximately 30 mTorr sec, forms a uniform tunnel barrier with a barrier height straight phi(b) of 1.2 eV. Greater O2 exposure does not alter straight phi(b) or the ballistic transmissivity of the oxide conduction band. Tunneling spectroscopy indicates a broad energy distribution of electronic states in the oxide. With increasing O2 dose the states below 1.2 eV gradually become localized, but until this localization is complete these states can provide low-energy single-electron channels through the oxide.

Journal Article↗
PubMed2001

Spintronics: a spin-based electronics vision for the future.

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

Journal Article↗
PubMed1988

Structure of superconducting thin films of YBa2Cu3O7-x grown on SrTiO3 and cubic zirconia.

Thin films of the superconductive oxide YBa2Cu3O7-x have been made by electron-beam coevaporation of the metals in an oxygen atmosphere onto single-crystal [001]-oriented SrTiO3 and yttria-stabilized zirconia (YSZ) substrates. The oxide films were superconducting in the as-deposited state (Tc = 81-83K, Jc = 10(6) A/cm2 at 4.2K). Bright-field imaging, selected-area diffraction (SAD), and high-resolution imaging in the transmission electron microscope were used to characterize the microstructure of these films. All of the films were polycrystalline. On SrTiO3 the films were oriented, for the most part, with [110] parallel to the substrate surface. On YSZ, two microstructures were observed: one with smaller rectangular grains oriented with (100) or (010) parallel to the substrate surface and the other with (001) parallel to the surface (i.e., c-axis up).

Computer Simulation↗