Magnetic Ordering in Doped Cd1-xCoxSe Diluted Magnetic Quantum Dots

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• 作者：Khalid M. Hanif ; Robert W. Meulenberg ; and Geoffrey F. Strouse
• 刊名：Journal of the American Chemical Society
• 出版年：2002
• 出版时间：September 25, 2002
• 年：2002
• 卷：124
• 期：38
• 页码：11495 - 11502
• 全文大小：163K
• 年卷期：v.124,no.38(September 25, 2002)
• ISSN：1520-5126

文摘

In this study, we report structural, vibrational, and magnetic data providing evidence of randomion displacement in the core of CdSe quantum dots on the Cd²⁺ sites by Co²⁺ ions (between x = 0 and0.30). Structural evidence for core doping is obtained by analyzing the powder X-ray diffraction (pXRD),data which exhibits a linear lattice compression with increasing Co²⁺ concentration, in accord with Vegard'slaw. Correlated with the pXRD shift, a hardening of the CdSe longitudinal optical phonon mode and a newlocal vibrational mode are observed which track Co²⁺ doping concentration. Consistent with the observedcore doping, superconducting quantum interference device (SQUID) measurements indicate a surprisingincrease for the onset of spin glass behavior by an order of magnitude over bulk Co:CdSe. Correlation ofSQUID results, pXRD, and Raman measurements suggests that the observed enhancement of magneticsuperexchange between Co²⁺ dopant ions in this confined system arises from changes in the nature ofcoupling in size-restricted materials.