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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Cheng, Shun-JenSubject: search.filters.subject.paramagnetism

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    Exposure of the Hidden Anti-ferromagnetism in Paramagnetic CdSe:Mn Nanocrystals
    (2015-01-01)
    Zou, Shou-Jyun
    ;
    Wang, Sheng-Tsung
    ;
    Wu, Ming-Fan
    ;
    Jian, Wen-Bin
    ;
    Cheng, Shun-Jen
    We present theoretical and experimental investigations of the magnetism of paramagnetic semiconductor CdSe:Mn nanocrystals and propose an efficient approach to the exposure and analysis of the underlying anti-ferromagnetic interactions between magnetic ions therein. A key advance made here is the development of an analysis method with the exploitation of group theory technique that allows us to distinguish the anti-ferromagnetic interactions between aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic-ion-doped semiconductor nanocrystals. By using the method, we clearly reveal and identify the signatures of anti-ferromagnetism from the measured temperature-dependent magnetisms and furthermore determine the average number of Mn2+ ions and the fraction of aggregative ones in the measured CdSe:Mn nanocrystals.
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    Magnetism of magnetic ion doped semiconductor nanocrystals
    (2013)
    Zou, Shou-Jyun
    ;
    Cheng, Shun-Jen
    ;
    電子物理學系
    ;
    Department of Electrophysics
    Magnetic ion-doped semiconductor nanocrystals (NCs) have recently drawn a great deal of interest because of the intriguing physical properties and the application potential in spintronics and magneto-electronics. In this work, we report on theoretical studies of magnetism in colloidal CdSe NCs doped with Mn2+ ions. Numerically, the exact diagonalization (ED) technique is employed to calculate the electronic structures and magnetizations of singly changed CdSe NCs doped with four Mn ions in various spatial distributions. The numerical results show that the magnetism in a few-Mn doped NC is not only determined by the total number of Mn ions, but also sensitively depends on the individual locations, which are however hardly considered by widely used mean field theory. Remarkably, the formation of Mn clusters in a NC leads to the significant deviation of the magnetization from the standard Brillouin function description for an ideal paramagnet. The quantum size effect is shown to enhance the magnetizations of magnetic NCs via the interactions between the quantum confined carriers and Mn-clusters. A solvable constant interaction model (CIM) with the consideration of individual Mn spins is presented for the explanation of the numerical data.
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    Paramagnetism of interacting few-electron quantum dot with single magnetic impurity
    (2006-05-01)
    Cheng, Shun-Jen
    ;
    電子物理學系
    ;
    Department of Electrophysics
    We present theoretical results on the effects of particle-particle interaction and single spin-(5)/(2) magnetic impurity (Mn(2+)) on the paramagnetism of interacting spherical quantum dots(QDs). Within the effective mass approximation, the energy spectrum, magnetization, and magnetic susceptibility of the semi-magnetic QDs with electron number N(e) = 1-4 are calculated by using the configuration interaction method. It is found that the sp-d coupling between carrier and Mn(2+) magnetic ion gives rise to suppression or enhancement of paramagnetism, sensitively depending on electron number and the location of ion. The magnetic properties of the dot with N(e) = 3,4 exhibit pronounced anisotropy due to the anti-symmetry character of the p-shell wave functions coupled to magnetic ion. (c) 2006 Elsevier B.V. All rights reserved.