No description available.

In this study, the samples were prepared with mixed two colossal magnetoresistance materials and sintered at high temperature. Then analysis the affect of doping concentration in MR effect, and applied it on the magnetic thin film. X-ray diffraction images and SEM images were used to show the lattice structure and grain boundary. The RT curves show the position of Tp temperature ,and pH curves shows the characteristic of MR.

The noise performances of Al2O3-based magnetic tunnel junctions (MTJs) in the low-frequency regime were systematically studied. Conetic alloy Ni77Fe14Cu5Mo4 was deposited as both the MTJ pinned layer and free layer due to its superb magnetically soft properties. The Al2O3-MTJ sensors with Conetic alloy exhibited a linear field response with a relatively small easy-axis coercivity of 3 Oe. A tunneling magneto-resistance (TMR)of 9.5% and Hooge parameter of 3.82 × 〖10〗^(-7)μm^2 were achieved without any hard-axis bias field. The hysteresis was removed by applying an external magnetic field of 8 Oe along the hard axis and the sensor sensitivity was 0.4%/Oe within a linear region at room temperature. The relation between the Hooge parameter and hard-axis field was investigated and the result illustrated that the 1/f noise could be suppressed by an optimized hard-axis bias field. Additionally, a rotating magnetic field was employed to investigate the angular dependence of the MTJ low-frequency noise. Measurement results indicated that the Hooge parameter was angular-dependent and exhibited a linear relation with respect to the angular magneto-resistive susceptibility. Also, it could be inferred that the Hooge parameter possessed a higher value when the Conetic MTJs were in the region of antiparallel state. These studies showed that it was feasible to use Conetic alloy as the soft magnetic layer in MTJ sensor for its small coercivity, and a hard-axis bias field could be used to linearize the sensor response and suppress the 1/f noise induced by the magnetic fluctuation in the MTJ ferromagnetic layers. Besides the study of low-frequency noise in MTJs, the feasibility of biomarker immunoassay with MTJ sensors is investigated. Initially, with the assistance of Al2O3-MTJ sensors with Conetic alloy, 20-nm iron-oxide magnetic nanoparticles (MNPs) with three different concentrations were successfully detected by the shift of the TMR curve. The maximum resistance deviation was 0.16 Ω for an MNP concentration of 20.0 mg/mL. Based on this study, the detection of alpha-fetoprotein (AFP) labeled with 20-nm iron-oxide MNPs together with MTJ sensors by a sandwich-assay configuration was further investigated. AFP is a vital hepatic tumor biomarker and the detection of AFP has significant applications for clinical diagnostics and immunoassay for early-stage liver cancer indication. To further increase the sensitivity, MgO-MTJ sensors with a TMR of 122% and sensitivity of 0.95%/Oe were employed. The target AFP antigens of three concentrations were detected, and experimental data indicated that the resistance variation of the MTJ sensor increased with the AFP concentration ratio proportionally, which was consistent with previous studies. These results conclusively demonstrate that MTJ sensors together with MNPs are a promising bio-sensing platform for biomarker immunoassay. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

No description available.

The ultimate intent of this research program is to produce nanosized magnetic tunneling junctions, and to study the physical properties of such devices. The physical phenomena of nanosized tunneling junctions are significantly different than that of currently popular micro-sized junctions. There is a considerable amount of work that must be done prior to producing these new junctions to ensure that good measurements can be carried out once the structures have been built. This thesis describes the efforts taken to design a measurement platform that will accurately measure tunneling magnetoresistance (TMR) in nanosized Magneto-tunneling Junctions (MTJ). The testing done with this system at various stages throughout the design and testing process confirm the expectations for the performance of the system. Voltage-current measurements can be performed on objects ranging from a few nanometers in size to micrometer sized. Traditional micro-sized MTJs have not been excluded in this design.

Zhou Lingzhao. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 84-85). / Text in English; abstracts in English and Chinese. / Zhou Lingzhao. / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Magnetoresistance effect --- p.1 / Chapter 1.2 --- Giant magnetoresistance (GMR) effect --- p.2 / Chapter 1.3 --- CMR effect in rare earth manganites --- p.2 / Chapter 1.4 --- Main research in this thesis --- p.5 / Chapter Chapter 2 --- Synthesis technology / Chapter 2.1 --- Conventional solid state reaction --- p.8 / Chapter 2.2 --- Powder preparation --- p.10 / Chapter 2.3 --- Shaping --- p.13 / Chapter 2.4 --- Sintering --- p.14 / Chapter 2.5 --- Fabrication method in this experiment --- p.20 / Chapter 2.6 --- Characterization method --- p.22 / Chapter Chapter 3 --- Stoichiometry problems in LCMO / Chapter 3.1 --- Doping effects in La2/3Ca1/3MnO3 --- p.24 / Chapter 3.2 --- La stoichiometry in La2/3Ca1/3MnO3 --- p.28 / Chapter 3.3 --- Mn stoichiometry in La2/3Ca1/3MnO3 --- p.28 / Chapter 3.4 --- Oxygen stoichiometry in La2/3Ca1/3MnO3 --- p.32 / Chapter Chapter 4 --- Search for binders in the synthesis of La2/3Ca1/3MnO3 / Chapter 4.1 --- Solid state reaction --- p.38 / Chapter 4.2 --- Density --- p.39 / Chapter 4.3 --- Crystal structure --- p.41 / Chapter 4.4 --- SEM analyses --- p.48 / Chapter 4.5 --- Resistivity and magnetoresistance --- p.54 / Chapter 4.6 --- Small polaron transport --- p.72 / Chapter 4.7 --- Conclusion --- p.81

"January 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstract in Chinese.

Wan King Tin = La2/3Ca1/3MnO3薄膜的各向異性磁致電阻 / 尹擎天. / Thesis submitted in: August 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Wan King Tin = La2/3Ca1/3MnO3 bo mo de ge xiang yi xing ci zhi dian zu / Yin Qingtian. / Acknowledgments --- p.i / Abstract --- p.ii / 論文摘要 --- p.iv / Table of Contents --- p.v / List of figures --- p.vii / List of tables --- p.xi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction to Colossal Magnetoresistance (CMR) --- p.1 / Chapter 1.2 --- Origin of CMR --- p.6 / Chapter 1.3 --- Anisotropic Magnetoresistance (AMR) of LCMO Thin Film --- p.8 / Chapter 1.4 --- Properties near Tc / Chapter 1.4.1 --- Sharpness of transition --- p.13 / Chapter 1.4.2 --- Expansivity --- p.16 / Chapter 1.5 --- The motivation of this work --- p.19 / References --- p.20 / Chapter Chapter 2 --- Experimental methods / Chapter 2.1 --- Preparation of LCMO thin films --- p.23 / Chapter 2.2 --- Measurement of resistance and anisotropic magnetoresistance --- p.25 / References --- p.30 / Chapter Chapter 3 --- Properties of anisotropic magnetoresistance of single layer LCMO thin film / Chapter 3.1 --- Magnetic Field dependence of AMR / Chapter 3.1.1 --- In-plane AMR --- p.31 / Chapter 3.1.2 --- Out-of-plane AMR --- p.55 / Chapter 3.2 --- Temperature dependence of AMR --- p.65 / Chapter 3.3 --- Effect of c axis alignment --- p.75 / Chapter 4.4 --- "Effect of thickness, sharpness and Tp to AMR and their correlations " --- p.83 / References --- p.101 / Chapter Chapter 4 --- AMR of LCMO/PCMO Multilayer --- p.102 / References --- p.113 / Chapter Chapter 5 --- Conclusion --- p.114 / References --- p.117

by Yang, Fei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / by Yang, Fei.