No description available.

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Ho Lai-yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 53-56). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Peierls Transition --- p.3 / Chapter 2.1 --- The Start of the Idea --- p.3 / Chapter 2.2 --- Peierls Transition in Second Quantization Representation --- p.5 / Chapter 2.3 --- Effect of Peierls Transition on an Antiferromagnetic Chain --- p.6 / Chapter 2.4 --- Evidence of Spin-Peierls Transition --- p.9 / Chapter 2.5 --- Materials with Spin-Peierls Transition --- p.11 / Chapter 3 --- Mean Field Calculations --- p.15 / Chapter 3.1 --- Jordan-Wigner Transformation --- p.15 / Chapter 3.2 --- Diagonalization of the XY Model --- p.17 / Chapter 3.3 --- Hartree-Fock Approximation --- p.19 / Chapter 3.4 --- Quantum Effect of Lattice --- p.21 / Chapter 4 --- Bosonization --- p.25 / Chapter 4.1 --- Continuum Limit --- p.25 / Chapter 4.2 --- Bosonization --- p.28 / Chapter 4.3 --- Relaxation of the Restriction on Lattice Distortion --- p.36 / Chapter 4.4 --- More Discussion on the Phase Hamiltonian --- p.39 / Chapter 4.5 --- Limitation of the Bosonization Technique and the Phase Hamil- tonian Approach --- p.41 / Chapter 5 --- Effect of Doping Impurities on Spin-Peierls Model --- p.43 / Chapter 5.1 --- Experimental Results --- p.43 / Chapter 5.2 --- Analytical Calculations of Doping Effect --- p.44 / Chapter 5.3 --- Criticism on the Calculations --- p.50 / Chapter 6 --- Summary and Conclusions --- p.52 / Bibliography --- p.53 / Chapter A --- Random-Phase Approximation --- p.57

The work detailed here is the development of simulations and fabrication techniques used for the construction of thin-film acoustic transducers for use in the parametric pumping of spin waves. The Mason Model, a 1-D equivalent circuit simulating the responses of multilayer acoustic transducers, is implemented using ABCD-parameters in MATLAB to determine the expected response from fabricated devices. The simulation is tested by varying device parameters and comparing the changes in device resonance response to those of prior published results. Three-layer thin-film acoustic transducers were also fabricated. These transducers use zinc oxide (ZnO) as a piezoelectric layer with aluminum (Al) electrodes. Construction is accomplished using the common thin-film fabrication techniques of sputtering, thermal evaporation, etching, and lift-off patterning processes. The response of the fabricated transducers is compared to that of the simulated response by observing the transducer's resonance frequency and characteristics. These results are used to validate the simulation and the transducer fabrication process. Finally, their usefulness for the design and fabrication of an acoustic spin wave amplification system is considered. / Graduation date: 2013

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Elbio Dagatto, Florida State University, Dept. of Physics. Title and description from dissertation home page (Nov. 21, 2003). Includes bibliographical references.

This thesis explores finite-size effects on the spin-wave excitations of one-dimensional ferromagnetic and antiferromagnetic systems. Specifically, it presents a theoretical study of the scattering function, the physical observable in inelastic neutron and photon scattering experiments, under the influence of extra magnetic anisotropy energy localized at the system’s boundaries. The method for calculating spin wave scattering functions in bulk is adapted to the finite system case, enabling explicit numerical calculations with edge effects. Our results show a significant broadening of the scattering peaks of low energy spin waves in ferromagnetic and antiferromagnetic systems. We show that broadening is due to the emergence of spin excitations localized at the edge of the system, the so-called edge modes. / Graduate

No description available.

我們在實驗中實現以高頻磁場激發之自旋波發射源，此發射源不需外加直流磁場即可給出4GHz~13GHz頻率之自旋波。 使用自旋波為訊息載體的元件只有自旋角動量傳遞而沒有電荷流動，可以從根本上解決歐姆熱耗散問題，但在近期研究中自旋波的產生往往只能在FMR下伴隨產生，或因為波源的形狀而限制了自旋波頻率，然而在我們的實驗裡以共面波導產生垂直樣品面的高頻磁場，震盪鎳鐵合金(Permalloy﹐Ni81Fe19)線上之圓盤型結構。因強交換耦合作用與形狀異向性，圓盤型結構的鎳鐵合金會形成磁渦漩態(magnetic vortex)，且渦漩態中心會形成一塊垂直方向磁區，而此一磁區可以看作為點波源，此點波源即可解決頻率限制問題，且在這結構下不需直流外加場即可穩定存在，在高頻磁場震盪下即會傳播出自旋波。 由布里淵散射儀(Brillouin light scattering, BLS)量測中，我們觀察到此自旋波由圓盤向外發射，且可以由改變導入共面波導微波的頻率來調控自旋波的頻率，電性量測中證實此自旋波在特定磁場下magnetic vortex會有不同的本徵模式(eigen mode)震盪。 / The study of spin waves (SW) excitation in magnetic devices is one of the most important topics in modern magnetism due to promising applications as information carrier and for signal processing. However, a major challenge for this issue is the requirement to excite propagating spin waves with tunable GHz frequency in the magnonic circuits. We experimentally realize a spin-wave generator, capable of frequency modulation, in a magnonic waveguide. The emission of spin waves was produced by the reversal or oscillation of nanoscale magnetic vortex cores in a NiFe disk array. The vortex cores in the disk array were excited by an out of plane radio frequency (rf) magnetic field. The dynamic behaviors of the magnetization of NiFe were studied using a micro-focused Brillouin light scattering spectroscopy (BLS) setup and electrical measurement. In addition to the discrete ferromagnetic resonance (FMR) signals above external dc saturation magnetic field, we observed clear signals at zero magnetic field where vortex cores are present.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Mathematics. / Microfiche copy available in Archives and Science. / Bibliography: leaves 171-175. / Ph.D.