1/F Noise & slow spin dynamics in chromium, chromium alloys, and disordered iron zirconium
Michel, Richard Paul
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/18858
Description
Title
1/F Noise & slow spin dynamics in chromium, chromium alloys, and disordered iron zirconium
Author(s)
Michel, Richard Paul
Issue Date
1994
Doctoral Committee Chair(s)
Weissman, Michael B.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
spin dynamics
chromium
chromium alloys
iron zirconium
spin density wave polarization dynamics
Language
en
Abstract
1/f resistance noise studies of the spin dynamics in two magnetic systems
are described in this thesis. In chromium, 1 If noise was used as a probe to study
spin density wave polarization dynamics. Measurements of the noise
anisotropy in a high quality single crystal of Cr revealed a temperature range
where polarization dynamics were the dominant source of 1 If noise. In this
temperature range, discrete switching was observed in the resistance of
mesoscopic samples of Cr. This observation verified the existence of stable spin
density wave polarization domains. In CrMn the domain dynamics which were
found in the incommensurate SDW phase were absent in the commensurate
phase. This absence indicates that incommensurability plays a crucial role in the
polarization domain dynamics.
Amorphous FeZr undergoes two magnetic phase transitions which were
studied using 1 If noise. The first transition is from a paramagnetic to a
ferromagnetic phase. The noise observed in disordered FeZr films near T c was
non-linear and non-Gaussian and indicated the presence of fluctuating
ferromagnetic domains. The domains were sensitive to the small magnetic
fields induced by the ac probe current. At the temperature of the second
reentrant transition, Tf, the system enters a disordered spin glass phase. At Tf
the noise rose nearly an order of magnitude, and was linear and Gaussian. By
comparing the spectral slope and the temperature dependence of the noise near
T f , the degree to which the transition deviated from thermally activated
behavior was quantified. Measurements of the resistance noise in mesoscopic
constrictions of FeZr revealed interesting hydrogen motion in the system which
obscured the effects of the spin dynamics on the resistance.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.