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Fabrication of magnetic nanopillars ...

Andrews, Scott.

Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena.
Author:	Andrews, Scott.
Description:	88 p.
Notes:	Advisers: Joachim Stohr; Bruce Clemens.
Notes:	Source: Dissertation Abstracts International, Volume: 66-04, Section: B, page: 2129.
Contained By:	Dissertation Abstracts International66-04B.
Subject:	Physics, Electricity and Magnetism.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3171803
ISBN:	9780542087110

Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena.
Andrews, Scott.

Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena. - 88 p.

Advisers: Joachim Stohr; Bruce Clemens.

Thesis (Ph.D.)--Stanford University, 2005.

Spin-transfer torque, a magnetic phenomenon in which spin polarized currents can be used to alter the magnetic state of a ferromagnet. This torque can be used as the dominant switching mechanism in systems where the current density is high. However, at low current densities, this effect is overpowered by the Oersted field, the classical magnetic field created by an electric current. Unlike the spin-transfer torque which is proportional to the current density, the Oersted field is proportional to the total current. Thus, for the spin-transfer torque to be dominant, small structures are necessary. In an attempt to meet the design criteria of samples that would carry high current density but low total current, holes were drilled with focused ion beam (FIB) into silicon nitride films and filled with a stack of two ferromagnets separated by a nonmagnetic spacer. These samples were analyzed using x-ray photoemission electron microspectroscopy (X-PEEM). Due to magnetic uniformity issues in these samples, two other structures were subsequently investigated. One uses a stencil method that allows easy variations of the exact materials chosen. However, this sample design has the disadvantage that the magnetic material that should be switched using the spin polarized currents is not localized to the pillar structure being tested. This creates extraneous GMR signals during electrical measurements. Another sample, which was fabricated with the help of Hitachi, was designed to isolate the magnetic materials to a small region and does not show the convolved signal during electrical measurements. Both of these samples were analyzed with a scanning transmission x-ray microscope (STXM). Using a pump-probe configuration, the time dependent effects of the spin-torque transfer were examined. In the last sample, spin-transfer torque, combined with conventional Oersted switching, was observed and analyzed, Such a direct observation of spin injection and its time characteristics has never been achieved previously.

ISBN: 9780542087110Subjects--Topical Terms:

227483
Physics, Electricity and Magnetism.

Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena.
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245 1 0 $a Fabrication of magnetic nanopillars and X-ray imaging of spin-transfer phenomena.
300 $a 88 p.
500 $a Advisers: Joachim Stohr; Bruce Clemens.
500 $a Source: Dissertation Abstracts International, Volume: 66-04, Section: B, page: 2129.
502 $a Thesis (Ph.D.)--Stanford University, 2005.
520 # $a Spin-transfer torque, a magnetic phenomenon in which spin polarized currents can be used to alter the magnetic state of a ferromagnet. This torque can be used as the dominant switching mechanism in systems where the current density is high. However, at low current densities, this effect is overpowered by the Oersted field, the classical magnetic field created by an electric current. Unlike the spin-transfer torque which is proportional to the current density, the Oersted field is proportional to the total current. Thus, for the spin-transfer torque to be dominant, small structures are necessary. In an attempt to meet the design criteria of samples that would carry high current density but low total current, holes were drilled with focused ion beam (FIB) into silicon nitride films and filled with a stack of two ferromagnets separated by a nonmagnetic spacer. These samples were analyzed using x-ray photoemission electron microspectroscopy (X-PEEM). Due to magnetic uniformity issues in these samples, two other structures were subsequently investigated. One uses a stencil method that allows easy variations of the exact materials chosen. However, this sample design has the disadvantage that the magnetic material that should be switched using the spin polarized currents is not localized to the pillar structure being tested. This creates extraneous GMR signals during electrical measurements. Another sample, which was fabricated with the help of Hitachi, was designed to isolate the magnetic materials to a small region and does not show the convolved signal during electrical measurements. Both of these samples were analyzed with a scanning transmission x-ray microscope (STXM). Using a pump-probe configuration, the time dependent effects of the spin-torque transfer were examined. In the last sample, spin-transfer torque, combined with conventional Oersted switching, was observed and analyzed, Such a direct observation of spin injection and its time characteristics has never been achieved previously.
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