Electron transport and magnetoresistivity of In/Co nanoparticle composites

• Main Authors: Hsiao-Hui Kuan, 管曉慧
• Other Authors: Wen-Hsien Li
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/89meas

碩士 === 國立中央大學 === 物理研究所 === 96 === Indium nanoparticle was fabricated by thermal evaporation method .Sample purity and diameter were characterized by x-ray diffraction scheme. The analysis result show the pure 16 nm indium nanoparticle were obtained. No trace of impurity and oxidation was found. The result powder was mix with 28 nm cobalt with proper mass ratio, which defined as (In)X(Co)100-X(X=0,50,30,20,10). Temperature profile of electric transport properties of all samples were study by DC resistivity system. The measured curves were analysis both by tunneling and Mott’s VHR theory. The fitting result show Mott’s three-dimensional variable range hopping could well describe all resistivity cures, which implies the electric transport were implies three dimensional isotropic. The MR ratio of all samples at selective temperature was measured . Positive magnetoresistance (MR) at low applied magnetic fields to a negative MR at high fields were observed in our In/Co nanocomposites．This behavior is originated from Zeeman split of free electron level(ZMR).Two competitions mechanism is suggested .At first , the applied field described the electron levels into parallel and antiparallel the field, which caused lower hopping activation energy of high spin electrons. In the second, the applied field also reduce number of population of such electrons . So that , results positive to negative MR ratio transition.