Ag/Co奈米複合材料的電子傳輸探討; Transport behavior and magnetoresistance in Ag/Co nanocomposites

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题名:	Ag/Co奈米複合材料的電子傳輸探討;Transport behavior and magnetoresistance in Ag/Co nanocomposites
作者:	謝詩蔚;Shih-Wei Hsieh
贡献者:	物理研究所
关键词:	奈米複合材料;電子傳輸;磁阻;自旋極化電子穿隧模型;tunneling of spin-polarized electrons;magnetoresistance;nanocomposites
日期:	2004-06-25
上传时间:	2009-09-22 10:55:56 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	採用銀與鈷兩種奈米微粒，以各種不同質量比例調配之後均勻混合，施加不同的壓力壓合製成Ag/Co磁性奈米複合材料。利用不同的製作壓力調配銀與鈷奈米微粒之間距離大小及樣品空隙多寡，藉此討論磁性奈米複合材料的電子傳導機制。調配複合材料內銀與鈷奈米微粒質量比例，藉以改變樣品中的內部磁場，影響電阻隨著外加磁場改變，造成磁阻效應。量測樣品的磁化率與電阻率，發現低溫時具有磁阻效應，高溫磁阻效應則消失。且觀察到正磁阻效應在高磁場會轉折顯現出負磁阻效應。利用微粒系統的自旋極化電子穿隧模型，擬合樣品電阻率，解釋複合材料的磁阻轉折現象與內部電子在低溫的傳導機制，從而得到穿隧位壘的寬度。高溫電阻利用聲子散射效應擬合並解釋之。 Two kinds of nanoparticles, silver and cobalt, were mixed with different mass proportion, and exert different pressure to make the Ag/Co magnetic nanocompound material. In order to discuss the relation of the distance and the electron transport mechanism, we control the distance between the silver the cobalt nanoparticles ( the crevices in the sample ) by the different manufacturing pressures. The mass proportions of the nanoparticles change the internal magnetic field in the nanocompound material, and lead to the magnetoresistance. To measure the susceptibility and the resistivity, observing the magnetoresistance ( MR ) at low temperature, and the MR phenomenon vanishes at high temperature. We also observe that the positive MR transits to the negative MR at the high applied magnetic field. We use Sheng’s granular cobalt films model, tunneling of spin-polarized electrons, to explain the MR transition phenomenon and the electrons transport mechanism. And we obtain the width of potential barrier by fitting the resistivity curve of the samples. The phonon scattering effect explains the resistance at high temperature.
显示于类别:	[物理研究所] 博碩士論文

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