Atomic structure of (GeTe)m(Sb2Te3)n phase-change materials

Download
2014
Homurlu, Sibel
In this thesis, pulse phase resolved X-ray spectroscopy of four accretion powered millisecond pulsars which are IGR J00291+5934 , IGR J17498-2921 , XTE J0929-314 and XTE J1807-294 will be presented. Phase dependent changes during their outbursts will be checked for possible correlations of spectral parameters such as photon index and blackbody temperature with rotation phase using archive of Rossi X-ray Timing Explorer (RXTE) observations. In the analysis of IGR J17498-2921 in 2011 outburst , positive correlation is found between photon index and flux. In the analysis of XTE J0929-314 in 2002 outburst, negative correlation is found between photon index and blackbody temperature. In the analysis of XTE J1807-294 in 2003 outburst, about 150 days RXTE observation data is divided into 7 states, which consist of 3 flare and 4 non-flare states. In the first flare state analysis, negative correlation is found between blackbody temperature and photon index. In the second flare state analysis, positive correlation is found between blackbody temperature and photon index. In the second non-flare state analysis, positive correlation is found between flux and photon index. In the fourth non-flare state analysis, positive correlation is found between flux and photon index. On the other hand, correlation between blackbody temperature, photon index and flux is not found in the analysis of third flare state, first non flare state and third non-flare state analysis of XTE J1807-294 and in the analysis of IGR J00291+5934 in September 2008 outburst.

Suggestions

Pulse phase resolved x-ray spectroscopy of four accretion powered millisecond pulsars
Çolak, Sıdıka Merve; Baykal, Altan; Department of Physics (2014)
In this thesis, pulse phase resolved X-ray spectroscopy of four accretion powered millisecond pulsars which are IGR J00291+5934 , IGR J17498-2921 , XTE J0929-314 and XTE J1807-294 will be presented. Phase dependent changes during their outbursts will be checked for possible correlations of spectral parameters such as photon index and blackbody temperature with rotation phase using archive of Rossi X-ray Timing Explorer (RXTE) observations. In the analysis of IGR J17498-2921 in 2011 outburst , positive corre...
Investigation of the dynamic properties of ferroelectric crystals close to phase transitions
Kiracı, Ali; Erkoç, Şakir; Department of Physics (2015)
In this thesis we investigated the dynamical properties of some ferroelectric crystals and ceramics under various temperature and pressure conditions close to the phase transitions. In particular, we focused on the Raman frequencies, damping constant and the activation energy of soft modes with the pseudospin-phonon coupling in some ferroelectric crystals exhibiting phase transitions. We predicted the critical behavior of the frequency related to the order parameter (spontaneous polarization) in the ferroel...
First order and second order phase transitions in quartz and related materials
Lider, Mustafa Cem; Yurtseven, Hasan Hamit; Department of Physics (2017)
The mechanism of the phase transitions in quartz and in the related materials is investigated. First order and second order transitions are explained on the basis of various models using experimental data from literature. Inparticular, the Landau phenomenological theory is employed in terms of the order parameters and the temperature- pressure (T-P) phase diagram is constructed for those materials of interest. The sym- metry change of crystal structure is also analyzed by using group theory. The thermodynam...
Structural, electronic and magnetic properties of various nanosystems : molecular dynamics simulations and density functional theory calculations
Sholejh, Alaei; Erkoç, Şakir; Jalili, Seifollah; Department of Physics (2014)
In this study, we aim to investigate the structural, magnetic and electronic properties of various nanosystems using molecular dynamics simulation technique and density functional theory calculations. In the first part, iron oxide nanostructures (nanorods, clusters and nanoparticles) were considered. We applied strain, at different temperatures, on nanorods in order to study stability of iron oxide nanorods using molecular dynamics simulation. Furthermore, radial distribution functions of iron oxide nanopar...
Magnetic monitoring approach to kinetics of phase transformations in multicomponent alloy systems
Duman, Nagehan; Mekhrabov, O. Mekhrabov; Akdeniz, Mahmut Vedat; Department of Metallurgical and Materials Engineering (2012)
It is of great importance for a materials scientist both from fundamental and applicability aspects to have better understanding of solid-state phase transformations and its kinetics responsible for micro-/nano-structure development in alloys and corresponding physical and mechanical properties. Transformation kinetics can be analyzed by various experimental techniques such as thermal analysis, laborious electron microscopy combined with extensive image analysis or by measuring changes in electrical resisti...
Citation Formats
S. Homurlu, “Atomic structure of (GeTe)m(Sb2Te3)n phase-change materials,” M.S. - Master of Science, Middle East Technical University, 2014.