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Displaying 76 - 100 of 104

Second Harmonic Magneto-Resistive Imaging to Authenticate and Recover Data from Magnetic Storage Media

March 1, 2005
Author(s)
David P. Pappas, Alexey Nazarov, D Stevenson, Steven Voran, Mike E. Read, Erin M. Gormley, James Cash, Ken Marr, James Ryan
A scanning magneto-resistive (MR) microscope was developed for high resolution imaging of magnetic tapes and digital media. Second harmonic detection was used to remove thermal anomalies. We were able to image sufficient lengths of tape for authentication

Simultaneous state measurement of coupled Josephson phase qubits

February 25, 2005
Author(s)
Robert McDermott, Raymond Simmonds, Matthias Steffen, Ken B. Cooper, Katarina Cicak, Kevin Osborn, Seongshik Oh, David P. Pappas, John M. Martinis
One of the many challenges of building a scalable quantum computer is singleshot measurement of all the quantum bits (qubits). We have used simultaneous single-shot measurement of coupled Josephson phase qubits to directly probe interaction of the qubits

Zigzag-shaped magnetic sensors

December 13, 2004
Author(s)
Fabio C. da Silva, Willard C. Uhlig, Anthony B. Kos, Susan A. Schima, Joe Aumentado, John Unguris, David P. Pappas
Magnetism in zigzag-shaped thin-film elements is investigated using scanning electron microscopy with polarization analysis, magnetotransport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length

Observation of Quantum Oscillations between a Josephson Phase Qubit and a Microscopic Resonator using Fast Readout

October 25, 2004
Author(s)
Ken Cooper, Matthias Steffen, Robert McDermott, Raymond Simmonds, Seongshik Oh, Dustin Hite, David P. Pappas, John M. Martinis
We have detected coherent quantum oscillations between Josephson phase qubits and microscopic critical current fluctuators by implementing a new state readout technique that is an order of magnitude faster than previous methods. The period of the

Conducting atomic force microscopy for Nanoscale tunnel barrier characterization

August 13, 2004
Author(s)
Kristine Lang, Dustin Hite, Raymond Simmonds, Robert McDermott, David P. Pappas, John M. Martinis
Increasing demands on nanometer scale properties of oxide tunnel barriers necessitate a consistent means to assess them at these lengths. Here we use conducting atomic force microscopy (CAFM) to characterize aluminum oxide (AlOx)barriers to be used in

Decoherence in Josephson Qubits from Junction Resonances

August 13, 2004
Author(s)
Raymond Simmonds, Kristine Lang, Dustin Hite, David P. Pappas, John M. Martinis
We present experimental data that demonstrates a large reduction in the coherence of a Josephson phase qubit from spurious microwave resonances. These resonances are believed to arise from resonant fluctuators in the tunnel junction that couple to the

Arrays of magnetoresistive sensors for nondestructive testing

July 20, 2004
Author(s)
David P. Pappas, Fabio C. da Silva, Alexy V. Nazarov
Magnetic field distributions were measured for test stripline structures with anisotropic magnetoresistive (AMR), thin film Permalloy sensors. Linear arrays of eight barber-pole-type AMR sensors were used to increase the speed of the imaging and stability

Surface magnetic canting in a nonuniform film

January 1, 2004
Author(s)
M G. Pini, A Retlori, David P. Pappas, A. V. Anisimov, Alexander Popov
The zero temperature equilibrium configuration of a nonuniform system made of a ferromagnetic (FM) monolayer on top of a semi-infinite FM film is calculated using a nonlinear mapping formulation of mean-field theory, where the surface is taken into account

Zigzag Shaped Magnetic Sensors

January 1, 2004
Author(s)
S da, Willard C. Uhlig, A Kos, Joe Aumentado, Michael J. Donahue, John Unguris, David P. Pappas
Magnetism in zigzag shaped thin film elements is investigated using scanning electron microscopy with polarization analysis, magneto-transport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length

In-situ conductance characterization of Fe/Ag multilayer contacts on GaAs

July 1, 2003
Author(s)
Dustin Hite, Stephen E. Russek, David P. Pappas
Electrical transport characteristics for epitaxially grown Ag/Fe/Ag multilayers on GaAs(100) and GaAs(110) have been studied under various growth conditions. The surfaces and structure of the multilayer were characterized by low energy electron diffraction

Mechanisms for the multistep spin reorientation of ultrathin Fe films on Gd

March 31, 2003
Author(s)
A P. Popov, A. V. Anisimov, David P. Pappas
The multistep spin reorientation transition of ultrathin iron films on bulk gadolinium is described theoretically. We find that it is necessary to include cubic terms in the magnetic anisotropy energy expansion in order to explain this phenomenon

Magnetic Thin Film Interlaboratory Comparison

March 1, 2003
Author(s)
Fabio C. da Silva, David P. Pappas, C. M. Wang
A potential low magnetic moment standard reference material (SRM) was studied in an interlaboratory comparison. The mean and the standard deviation of the saturation moment m s, the remanent moment m r, and the intrinsic coercivity H c of nine samples were

Consideration of possible mass and velocity corrections to magnetic experiments

January 1, 2003
Author(s)
Z. Y. Liu, P. A. Dowben, A P. Popov, David P. Pappas
Gadolinium occurs, in natural abundance, as several isotopes. The possible combinations of different gadolinium isotopes dictates that even for a fixed number of atoms in the cluster, clusters of gadolinium atoms will exhibit a range of masses. This and

Spin polarization of injected electrons

May 17, 2002
Author(s)
W F. Egelhoff, M D. Stiles, David P. Pappas, D T. Pierce, J M. Byers, M B. Johnson, B T. Jonker, Jose E. Alvarellos, J G. Gregg, J A. Bland, R Buhrman

Spin Polarization of Injected Electrons

May 17, 2002
Author(s)
William F. Egelhoff Jr., Mark D. Stiles, David P. Pappas, S Alvarado, J Gregg, J Bland, R A. Buhrman, Daniel T. Pierce, J Byers, M Johnson, B Jonker
A recent paper in Science made the claim of 92% polarization for the injection spin polarized electrons from a Ni scanning tunneling microscopy (STM) tip into GaAs(110). Actually they state their result as 92% efficiency for the injection of 100%

Spin Polarization of Injected Electrons

May 1, 2002
Author(s)
William F. Egelhoff Jr., Mark D. Stiles, David P. Pappas, Daniel T. Pierce, J M. Byers, J M. Johnson, B T. Jonker, S F. Alvarado, J F. Gregg, J A. Bland, R Buhrman
A recent paper in Science made the claim of 92% polarization for the injection spin polarized electrons from a Ni scanning tunneling microscopy (STM) tip into GaAs(110). Actually they state their result as 92% efficiency for the injection of 100%

Surface magnetic phase diagram for a semi-infinite ferromagnet

October 12, 2001
Author(s)
Pavel Kabos, David P. Pappas
The phase diagram for the orientation of the surface region is calculated in the parameter space defined by the surface and bulk anisotropy in semi-infinite ferromagnetic systems and in thin ferromagnet films. Surface magnetic canting always occurs when

Second Harmonic Magneto-Resistive Imaging to Authenticate and Recover Data From Magnetic Storage Media

March 1, 2001
Author(s)
David P. Pappas, C S. Arnold, G Shalev, C Eunice, D Stevenson, Steven Voran, Mike E. Read, Erin M. Gormley, James Cash, Ken Marr, James Ryan
A scanning magneto-resistive microscope was developed that allows for high resolution imaging of magnetic tapes and digital media. By using second harmonic detection to remove thermal anomalies we are able to image sufficient lengths of tape for