Brillouin scattering from single-crystal dysprosium and gadolinium films

"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."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Kong, Steven Hin-Chung

Contributors dc:contributor

• Klein, Miles V.

• brillouin scattering
• single-crystal dysprosium
• gadolinium films
• magnetic continuum models

Statement dc:rights

• 1992 Steven Hin-Chung Kong

Language dc:language

en

Identifier

3469570

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/18913