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Search Publications by: Stephen E. Russek (Fed)

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Displaying 51 - 75 of 170

Spin-transfer dynamics in spin valves with out-of-plane magnetized CoNi free layers

January 29, 2010
Author(s)
William H. Rippard, Alina M. Deac, Matthew R. Pufall, Justin M. Shaw, Mark W. Keller, Stephen E. Russek, Gerrit E. Bauer, Claudio Serpico
We have measured spin-transfer-induced dynamics in magnetic nanocontact devices having a perpendicularly magnetized Co/Ni free layer and an in-plane magnetized CoFe fixed layer. The frequencies and powers of the excitations agree well with the predictions

Magnetic Noise in a Low-Power Picotesla Magnetoresistive Sensor

October 25, 2009
Author(s)
Stephen E. Russek, Lu Yuan, Sean Halloran, Fabio C. da Silva, David P. Pappas, John M. Moreland, Sy-hwang Liou, Rui Zhang
We present a design of a low power, compact, magnetoresistive sensor. The key features of the design are(1) decreasing the noise by the use of a 64 element magnetic tunnel junction (MTJ) bridge,(2) reducing the magnetic noise by annealing the MTJ sensors

Temperature dependence of spin-torque-driven self-oscillators

October 15, 2009
Author(s)
William H. Rippard, Matthew R. Pufall, Thomas Cecil, Thomas J. Silva, Stephen E. Russek, M. L. Schneider
We have measured the temperature dependence of spin-torque-driven self-oscillations in point-contact nanooscillators for both in-plane and out-of-plane applied fields. We find that the linewidth for both field geometries is qualitatively similar. In the

Reversal mechanisms in perpendicular magnetic nanostructures

July 16, 2008
Author(s)
Justin M. Shaw, Stephen E. Russek, Michael J. Donahue, Thomas Thomson, Bruce Terris, Michael Schneider, Miles Olsen
We find that the reversal mechanism in magnetic nanostructures is highly dependent on the nature and condition of the edges. Temperature and size dependent reversal properties of fabricated perpendicularly magnetized nanostructures down to 25 nm in

Spin Transfer Precessional Dynamics in Co 60 Fe 20 B 20 Nanocontacts

March 14, 2008
Author(s)
William H. Rippard, Matthew R. Pufall, Michael L. Schneider, Kevin Garello, Stephen E. Russek
We report on the precessional dynamics in spin transfer oscillators having Co 60Fe 20B 20 free layers as a function of annealing time at 225 °C. Repeated annealing reduces the critical current I c by roughly a factor of 3 and increases the tunability of

Dependence of noise in magnetic tunnel junction sensors on annealing field and temperature

March 7, 2008
Author(s)
Stephen E. Russek, David P. Pappas, Sean Halloran, Lu Yuan, Sy-Hwang Liou, Rui Zhang
The minimum detectable field of magnetoresistive sensors is limited by their intrinsic noise. Magnetization fluctuations are one of the crucial noise sources and are related to the magnetization alignment at the antiferromagnetic – ferromagnetic interface

Low-field current-hysteretic oscillations in spin-transfer nanocontacts

April 19, 2007
Author(s)
Matthew Pufall, William Rippard, Michael Schneider, Stephen E. Russek
We have measured spin-transfer-driven, large-amplitude, current-hysteretic, low frequency (less than or equal to} 500 MHz), narrowband oscillations in nanocontacts made to spin valve structures. The oscillations occur in zero field, persist up to 5 mT for

Broadband Electrical Characterization of Multiwalled Carbon Nanotubes and Contacts

March 22, 2007
Author(s)
Paul Rice, T. M. Wallis, Stephen E. Russek, Pavel Kabos
We have welded an individual multiwalled carbon nanotube (MWNT) onto a microlithographically-patterned coplanar waveguide (CPW) and measured the electrical response of the nanotube and the contacts from 100 MHz to 24 GHz. The MWNT was welded to the CPW in

Broadband Electrical Characterization of Multiwalled Carbon Nanotubes and Contacts

March 22, 2007
Author(s)
Thomas M. Wallis, Stephen E. Russek, Pavel Kabos, Paul Rice
The electrical response of an individual multiwalled carbon nanotube (MWNT) and its contacts, welded to a coplanar waveguide (CPW), was measured up to 24 GHz using a technique that removes environment effects. This is the first time MWNT contact effects

Thermal effects on the critical current of spin torque switching in spin valve nanopillars

February 28, 2007
Author(s)
Michael Schneider, Matthew Pufall, William Rippard, Stephen E. Russek, Jordan A. Katine
In spin valve nanopillars, temperature affects the spin torque reversal of the free magnetic layer. The authors compare values of zero temperature critical switching current I c0 extrapolated from room temperature pulsed current switching measurements to

Origins of switching field distributions in perpendicular magnetic nanodot arrays

January 19, 2007
Author(s)
Justin Shaw, William Rippard, Stephen E. Russek, Tim Reith, Charles M. Falco
We studied the reversal properties of perpendicularly magnetized Co/Pd nanodots from 100 to 50 nm in diameter fabricated using electron beam lithography. Polycrystalline Co/Pd multilayers show considerable differences in the switching field distribution

Manipulation of magnetic particles by patterned arrays of magnetic spin-valve traps

December 20, 2006
Author(s)
Elizabeth Mirowksi, John M. Moreland, Stephen E. Russek, Michael J. Donahue
A novel magnetic for microfluidic manipulation of magnetic particles is discussed. The particles are confined by an array of magnetic spin valves with bistable ferromagnetic "ON" and antiferromagnetic "OFF" net magnetization states. The switchable fringing

Dynamic Lorentz Microscopy of Micromagnetic Structure in Magnetic Tunnel Junctions

November 20, 2006
Author(s)
Justin Shaw, R.H. Geiss, Stephen E. Russek
Lorentz microscopy was used to study the micromagnetic structure and magnetization reversal in magnetic tunnel junctions (MTJs) fabricated with different processing conditions including a preoxidation process. The authors find that the free layer in a MTJ

Experimental separability of channeling giant magnetoresistance in Co/Cu/Co

July 13, 2006
Author(s)
William E. Bailey, Stephen E. Russek, X.-G. Zhang, W. H. Butler
The magnitude of the electronic channeling contribution is a significant open issue in the understanding of giant magnetoresistance (GMR). We show that for the technologically important system Co/Cu/Co, channeling GMR can be isolatedand quantified

Tailored Nanoscale Contrast Agents for Magnetic Resonance Imaging

December 30, 2005
Author(s)
Alexander J. Barker, Brant Cage, Stephen E. Russek, Ruchira Garg, R Shandas, Conrad Stoldt
Two potential molecular imaging vectors are investigated for material properties and magnetic resonance imaging (MRI) contrast improvement. Monodisperse magnetite (Fe 3O 4) nanocrystals ranging in size from 7 to 22 nm are solvothermally synthesized by

Ultraviolet Laser Damage of Carbon Nanotube Coatings on Thermal Detector Platforms

November 14, 2005
Author(s)
Darryl A. Keenan, Natalia Varaksa, Anne Dillon, Chaiwat Engtrakul, Stephen E. Russek, John H. Lehman
We have initiated a program to demonstrate the next generation of optical detector coatings using carbon nanotubes (CNTs). These coatings have been used on a variety of detector platforms for laser power and energy measurement standards. These coatings

Mutual phase-locking of microwave spin torque nano-oscillators

September 15, 2005
Author(s)
Shehzaad F. Kaka, Matthew Pufall, William Rippard, Thomas J. Silva, Stephen E. Russek, Jordan A. Katine
The spin torque effect that occurs in nanometre-scale magnetic multilayer devices can be used to generate steady- state microwave signals in response to a d.c. electrical current. This establishes a new functionality for magneto-electronic structures that

Resonant microwave power absorption and relaxation of the energy levels of the molecular nanomagnet Fe 8 using superconducting quantum interference device-based magnetometry

August 15, 2005
Author(s)
Brant Cage, Stephen E. Russek, David Zipse, Micah North, Naresh S. Dalal
Energy levels and saturation of molecular nanomagnet Fe 8 crystals were investigated using a 95 and 141 GHz electron paramagnetic resonance (EPR) technique based on a standard superconducting quantum intererence device (SQUID) magnetometer. The technique