Orbital susceptibilities of PbSe quantum dots

• Main Authors: Sen-Jen Chiang, 江森正
• Other Authors: Wen-Bin Jian
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/95681223858229203230

碩士 === 國立中興大學 === 物理學系 === 93 === Different sizes of PbSe spherical quantum dots have been synthesized for the study of magnetic properties on the nanometer scale. The measurements of temperature and field dependences of susceptibilities were performed by using a SQUID magnetometer. Two kind of orbital susceptibilities were observed, including the Curie and the finite-size correction to the Landau susceptibilities. The Curie susceptibility was observed in the temperature dependence of magnetic susceptibilities at low temperature. The Curie term comes from the quantum dots instead of the PbSe atom. The observed Curie susceptibility disappeared as increasing the temperature. The positive susceptibility value in high temperature is not the contribution of Curie susceptibility, but from the finite-size correction to the Landau susceptibility. The field dependence of differential susceptibility shows zero-field paramagnetic peak and reveals finite-size corrections to the Landau susceptibility. Both the two kinds of orbital susceptibilities display linear dependence on the size of the quantum dot. We also have observed an interesting ferromagnetic phenomena. The hysteresis loops of PbSe quantum dots exist even at room temperature.