Effect of double-cation substitution on the low-energy electrodynamics of M-type hexaferrites/Влияние двухкатионного замещения на низкоэнергетическую электродинамику гексаферритов М-типа Ахмед Асмаа Гамаль Мохамед

Короткий опис

Оглавление диссертациикандидат наук Ахмед Асмаа Гамаль Мохамед
Table of Contents
Acknowledgments
List of Abbreviation and Symbols
Introduction
Chapter 1. Crystal structure, properties, and applications of M-type hexaferrites
Preface
1.1 Crystal structure of hexaferrites
1.1.1 Crystal structure of barium M-type hexaferrites
1.1.2 Building blocks of the barium M-type hexaferrite lattice
1.2 Tunable barium M-type hexaferrite for practical applications
1.2.1 Multiferroics properties of barium M-type hexaferrites
1.2.2 Soft mode phenomena
Chapter 2. Experimental section
2.1 Samples characterization and preparation
2.1.1 Single crystals
2.1.2 Ceramics
2.2 Dielectric spectroscopy techniques
2.2.1 Fourier transform infrared spectroscopy (FTIR)
2.2.2 Terahertz spectroscopy
2.2.2.1 Monochromatic terahertz backward-wave oscillators (BWOs)
2.2.2.2 Terahertz time domain spectrometers (THz-TDS) ''TeraView TPS Spectra-3000'' and ''Menlo Systems Tera K15''
2.2.3 Impedance spectroscopy
2.3 Data analysis of the dielectric spectra
2.3.1 The independent Lorentzian model
2.3.2 Terahertz spectra analysis methods
2.3.3 The dielectric relaxation time x(t)
Chapter 3: Broadband electrodynamic response of single-crystalline Ba1-xPbxFe12O19
Preface
3.1 Infrared spectroscopy
3.1.1 Middle-infrared spectra of single-crystalline Ba1-xPbxFe12O19
3.1.2 Infrared phonon resonances observed in single-crystalline Ba^PbiFe^Ow
3.1.3 Infrared dielectric response of single-crystalline Ba1-xPbxFe12O19
3.2 Terahertz spectroscopy
3.2.1 Terahertz transmissivity spectra of single-crystalline Bai-xPbxFei2Oi9
3.2.2 The dielectric nature of the absorption resonances in lead-substituted barium M-type hexaferrite
3.2.3 Terahertz dielectric permittivity spectra in lead substituted barium M-type hexaferrite
3.2.4 Terahertz ferroelectric-like soft mode
3.2.5 Gigahertz resonance in lead-substituted barium M-type hexaferrite
3.3 Radio-frequency spectroscopy
3.3.1 Dielectric relaxations in radio-frequency spectra of Bai-xPbxFei2Oi9
3.3.2 Temperature dependence of dielectric relaxation spectra of Ba1-xPbxFe12O19 crystals
Summary
Chapter 4: Terahertz electrodynamic response of Ba1-xPbxFenO19 ceramics
Preface
4.1 Transmissivity and reflectivity spectra of Ba1-xPbxFe12O19 ceramics
4.2 Complex dielectric permittivity spectra of Ba1-xPbxFe12O19 ceramics
4.3 Terahertz soft phonon observed in Ba1-xPbxFe12O19 ceramics
4.4 Terahertz soft mode observed in Ba1-xPbxFe12O19 ceramics
4.5 Molecular model of the soft mode
Summary
Chapter 5. The influence of double-cation substitution on low-energy electrodynamics of
barium hexaferrite
Preface
5.1 Infrared spectroscopy of single-crystalline Ba0.20Pb0.80AlyFe12-.yO19
5.2 Terahertz spectroscopy of single-crystalline Ba0.20Pb0.80AlyFe12-yO19
5.2.1 Temperature dynamics of low-energy(terahertz) absorption lines
5.3 Crystal field distortions
Summary
Conclusions
Bibliography
Appendix A
Appendix B