Brillouin scattering from single-crystal dysprosium and gadolinium films
Kong, Steven Hin-Chung
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/2142/18913
Description
Title
Brillouin scattering from single-crystal dysprosium and gadolinium films
Author(s)
Kong, Steven Hin-Chung
Issue Date
1992
Doctoral Committee Chair(s)
Klein, Miles V.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
brillouin scattering
single-crystal dysprosium
gadolinium films
magnetic continuum models
Language
en
Abstract
"Brillouin light scattering studies have been made on the temperature dependence and
dispersion of long-wavelength acoustic phonons in single-crystal Dy films and longwavelength
acoustic magnons in single-crystal Gd filins. The spectra were analyzed by
using elastic and magnetic continuum models for the Dy and Gd systems, respectively.
The room temperature dispersion and the temperature dependence of the velocities
of surface and guided acoustic waves have been studied in c-axis single-crystal Dy films
grown on sapphire substrates with Nb (or Ta) and Y buffer layers. The room temperature
data compared very well with the dispersion of acoustic phonon velocities calculated using
the bulk elastic constants in the elastic model. We observed modest anomalies in the
temperature dependences for the velocities of acoustic waves inDy films and bulk Dy.
However, we observed a very large anomaly in the temperature dependence of the relative
peak intensities in the Brillouin spectra for the 450A Dy film. It was concluded that changes
in the elastic constants of the Dy layer by itself is unlikely the cause of this large anomaly,
and it may be due to interactions with the magnetic system.
Two bulk acoustic magnons and one shallow surface magnon were observed in a
300A c-axis Gd film. The temperature dependence of the frequencies of these magnons
was shown to depend on the bulk values of the c-axis magnetic stiffness constant De,
defined by ro(q) = ""'LDiqi2 where lqal << 1, and the axial-anisotropy constant P2 ,
defined by H aniso. = P 2(Sz)2+ • • • . From the Brillouin data and the magnetization of the
Gd film determined by a SQUID magnetometer, the values of Dc(T) and P2(T) were
extracted over limited temperature ranges. These values are shown to be consistent with
bulk values from the literature."
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.
