Jung-Il Park

Magnetic Properties of Cr-doped LiNbO₃ by Using the Projection Operator Technique

The electron spin resonance lineshape (ESRLS) function for the electron spin resonance linewidth (ESRLW) of Cr³? (S = 3/2) in ferroelectric lithium niobate single crystals doped with 0.05 wt% of Cr, is obtained by using the projection operator technique (POT), developed by Argyres and Sigel. The ESRLS function is calculated to be axially symmetric about the c ? axis and analyzed by using the spin Hamiltonian H SP = μB (BㆍgㆍS) + SㆍDㆍS with the parameters g = 1.972 and D = 0.395 ㎝?¹. In the ca plane, the linewidths show a strong angular dependence, whereas in the ab plane, they are independent of the angle. This result implies that the resonance center has an axial symmetry along the c ? axis. Further, from the temperature dependence of the linewidths that is shown, it can be seen that the linewidths increase as the temperature increases, at a frequency of v = 9.27㎓. This result implies that the scattering effect increases with increasing temperature. Thus, the POT is considered to be more convenient to explain the scattering mechanism as in the case of other optical resonant systems.

Application of a Continued-Fraction-Based Theory to Line-Profile in Mn-Doped GaN Film

Starting with the Kubo formalism and using the projection operator technique (POT) introduced by Kawabata, the optical quantum transition line-profiles (QTLPs) formula for a Mn-doped wurtzite GaN film was derived as a function of temperature at a frequency of 9.49 GHz (X-band), on the basis of continued fraction representation (CFR) which is a counterpart of the conventional series expansion (CSE). Utilizing this formula we obtained the fine-structure parameter a - F = 9.4 ×10-4 cm-1 and fitting parameter ζ= 4.1. The optical quantum transition half-widths (QTHWs) obtained with the use of these parameters agrees quite well with the existing experimental result in the temperature region T > 20 K. The QTHWs increase with increasing temperature due to the interaction of electrons with optical phonons. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition problems.

Thermal Properties of Mn-doped LiNbO3 Crystals from Magneto-Optical Transitions

In this study, we determine that the electron paramagnetic resonance line-width (EPRLW) is axially symmetric about the c-axis and analyze the spin Hamiltonian with an isotopic g-factor of 1.9920 at a frequency of 9.5 GHz. It should be noted that the electron paramagnetic resonance signals are Lorentzian. Our findings show that the EPRLW decreases exponentially with an increase in the temperature; i.e., its temperature dependence in the range 300-400 K obeys Arrhenius behavior, this kind of temperature dependence indicates an off-center a motional narrowing of the spectrum when Mn 2+ impurity ions substitute for Nb 5+ ions. The specific heats follow a linear dependence suggesting a simple Debye T 3 behavior.

Investigation of the Hyperfine Structure Effect in a Mn-Doped LiNbO 3

The computer program (EPR-NMR program version 6.2) employed here sets up the spin Hamiltonian matrices and determines their eigenvalues using exact diagonalization. We study the electron spin resonance for in ferroelectric single crystals. The self-energy is obtained using the projection operator method developed by Argyres and Sigel. The self-energy is calculated to be axially symmetric about the by the spin Hamiltonian. The line-widths decreased as the temperature increased; we assume that the hyperfine structure transition is a more dominant scattering than the other transitions. We conclude that the calculation process presented in this study is useful for quantum optical transitions.

Line-profile Formula in the Carbon Nanotubes by Electron Spin Resonance

Abstract : The line-width of carbon nanotubes (CNTs) was studied as a function of the temperature at a frequency of 9.49 GHz in the presence of external electromagnetic radiation. The relative frequency dependence of the absorption power is obtained with the projection operator technique (POT) proposed by Kawabata. The line-width increased as the temperature increased in the high-temperature region (T>200 K). The scattering is little affected in the low-temperature region (T<200 K) because there is no correlation between the resonance field and the Fermi-Dirac distribution function. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition problems. Keywords: ESR, CNTs, Projection operator, Line-profile, Line-widths, INTRODUCTION Electron spin resonance (ESR) spectroscopy has been used to assess the quality of carbon nanotube, CNT. 1 In ESR experiments, one applies a static magnetic field and measures the absorption power of electromagnetic radiation polarized perpendicular to the field direction. In the absence of SU(2) spin symmetry breaking terms in the system Hamiltonian, the absorption power is then simply

Investigation of Temperature Dependence for CNT Semiconductor in External Magnetic Field

We calculated the electron spin resonance (ESR) line-profile function. The line-width of single-walled carbon nanotube (SWNT) was studied as a function of the temperature at a frequency of 9.5 GHz in the presence of external electromagnetic radiation. The temperature dependence of the line-widths is obtained with the projection operator method (POM) proposed by Argyres and Sigel. The scattering is little affected in the low-temperature region (T

Electron Spin Transition Line-width of Mn-doped Wurtzite GaN Film for the Quantum Limit

Starting with Kubo’s formula and using the projection operator technique introduced by Kawabata, EPR lineprofile function for a Mn 2+ -doped wurtzite structure GaN semiconductor was derived as a function of temperature at a frequency of 9.49 GHz (X-band) in the presence of external electromagnetic field. The line-width is barely affected in the low-temperature region because there is no correlation between the resonance fields and the distribution function. At higher temperature the line-width increases with increasing temperature due to the interaction of electrons with acoustic phonons. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition systems.

Magneto-optical Properties of 55 Mn-doped SrTiO 3 Single Crystal

We calculated the EPR (electron paramagnetic resonance) line-shape function. The line-widths of a -doped single crystal was studied as a function of the temperature with 0.5 and 2 at. at a frequency of (X-band). The line-width decreases with increasing temperature, such temperature behavior of the line-width can indicate a motional narrowing of the spectrum, when impurity ions substitute for host ions in an off-center position, and thus there can be fast jumping of dipoles between several symmetrically equivalent configurations. Therefore, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition problems.

The Study of Phase-change with Temperature and Electric field in Chalcogenide Thin Film

We have been investigated phase-change with temperature and electric field in chalcogenide GeSbTe5/ thin film. Tc/(crystallization temperature) is confirmed by measuring the resistance with the varying temperature on the hotplate. We have measured I-V characteristics with GeSbTe5/ chalcogenide thin film. It is compared with I-V characteristics after impress the variable pulse. The pulse has variable height and duration.