Micromagnetic investigation of MnAs thin films on GaAs surfaces [Elektronische Ressource] / von Jyoti Ranjan Mohanty

Jyoti Ranjan Mohanty

Sujets

• Physik

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2005
• Nombre de lectures: 32
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Micromagnetic investigation of MnAs thin
lms on GaAs surfaces
DISSERTATION
zur Erlangung des akademischen Grades
doctor rerum naturalium
(Dr. rer. nat.)
im Fach Physik
eingereicht an der
Mathematisch-Naturwissenschaftlichen Fakultat I
Humboldt-Universitat zu Berlin
von
Herr M.Tech. M.Sc. Jyoti Ranjan Mohanty
geboren am 20.03.1976 in Tirtol, Indien
Prasident der Humboldt-Universitat zu Berlin:
Prof. Dr. Jurgen Mlynek
Dekan der Mathematisch-Naturwissenschaftlichen Fakultat I:
Prof. Thomas Buckhout, Ph.D.
Gutachter:
1. Prof. Dr. K. H. Ploog
2. Prof. Dr. T. Masselink
3. Prof. Dr. K. R. A. Ziebeck
eingereicht am: 18.03.2005
Tag der mundlichen Prufung: 15.06.2005 Abstract
This work presents the study of the micromagnetic domain structure and the
coupled magneto-structural phase transition of MnAs thin lms on GaAs.
In particular, the inuence of substrate orientation, lm thickness and ex-
ternal magnetic eld on the magnetic and structural properties are investi-
gated, employing the complementary measurement techniques atomic force
microscopy-AFM/magneticforcemicroscopy-MFMandlowenergyelectron
microscopy-LEEM / X-ray magnetic circular dichroism photoemission elec-
tron microscopy-XMCDPEEM for the characterization of the structural /
micromagnetic properties of the materials system.
MnAs exhibits a rst-order phase transition from the hexagonal, ferro-
magnetic -phase to the orthorhombic, paramagnetic -phase at around
40 C. In epitaxial MnAs lms on GaAs, it is known that the ferromag-
netic and the paramagnetic phases coexist over a wide temperature range of
about 30 C below the phase transition temperature. In this temperature
range, MnAs lms on GaAs (001) and (311)A substrates show a regular ar-
ray of ferromagnetic stripes due to the involved strain. The width of the
ferromagnetic stripes can be tuned by varying the temperature, whereas the
periodicity of the stripe pattern is found to be a linear function of lm thick-
ness. Theinpartcomplexmicromagneticdomainstructurestronglydepends
on the width and the distance of the ferromagnetic stripes, as it directly af-
fects the shape anisotropy and magnetic coupling, respectively. The