Influence of Mn ion on magnetism in Cd1-xMnxSe nanocrystals

• Main Author: 陳怡然
• Other Authors: 簡紋濱
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/84518933755178722783

碩士 === 國立交通大學 === 電子物理系所 === 97 === Semiconductor nanocrystal has been widely studied in last two decades, not only because the novel physical properties it has but also the potential of been building block of nanodevice. To modify semiconductor nanocrystal’s physical properties, doping impurities in nanocrystal is a widely used approach. Magnetic ion doped semiconductor nanocrystal, named diluted magnetic semiconductor nanocyrstal (DMSNC), such like Cd1-xMnxSe, Cd1-xMnxTe etc., has attracted scientists attention in recent years because of its potential of been new building block of nanodevice and combination of magnetic , electrical, and optical properties. Although the optical properties in this kind of material have been widely studied and the magnetic properties have been discussed in theoretical approach, the experimental study of magnetic properties in DMSNC is still lack. In this article, the magnetic properties of Cd1-xMnxSe nanocrystal with different size (d=5, 8 nm) and concentration (x=0.375 %, 0.15 %) have been studied by using SQUID magnetometer. Magnetic field dependence of magnetization (M-H curves) has been measured under 2 K and temperature dependence of magnetic susceptibility (χ-T curves) has been measured under external magnetic field in 100 Oe. The non-saturated phenomenon has been observed in all of the M-H curves. This phenomenon has been more manifest in higher concentration sample. We also observed that Curie law can not explain the χ-T curves of all of our samples because the nonzero magnetic susceptibility under high temperature region. After considering the Pauli paramagnetism comes from the free carriers in nanocrystals, we observed that, in lower concentration samples, magnetic properties could be explained by a summation of magnetic properties come from the Mn ions and the free-carriers in nanocrystal. However, in higher concentration samples, the Mn ions will affect the magnetic properties of free-carriers in nanocrystal thus making the magnetic properties more complex.