Exchange-bias phase diagram of CoO/Co/Si(111) and magnetic properties of Co/Ag-Si √3×√3/Si(111)

• Main Author: 許志榮
• Other Authors: 蔡志申
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/14394464097149320427

碩士 === 國立臺灣師範大學 === 物理學系 === 99 === In this thesis, we focus on the physical properties of CoO/Co/Si(111) and Co/Ag-Si √3 × √3/Si(111) systems. For CoO/Co/Si(111) with CoO thickness between 5 and 15 monolayers (ML), a phase diagram of the exchange bias has been established by way of comparing the results of zero-field cooling and field cooling. For CoO thinner than 10 ML, enhanced coercivity is observed because of the existence of nano-sized CoO particles at the interface. For CoO thicker than 15 ML, non-zero exchange field is observed because the magnetic anisotropy is large enough. For a Co/Ag-Si √3 × √3/Si(111) system, Co overlayer has been deposited on the top of Ag-Si √3 × √3/Si(111) surface alloy. For Co thinner than 4.38 ML, no Kerr signal is detected in the longitudinal configuration. The easy axis of magnetization for Co/Ag-Si √3 × √3/Si(111) is in the surface plane. By extrapolating the data for Kerr signal versus the Co thickness, the zero intercept shows no magnetic dead layer. This shows that the Ag-Si √3 × √3/Si(111) surface alloy is efficient for preventing the silicide formation between the Co layer and the silicon substrate. From the cryogenic treatments of the specimens, the Curie temperature of 3.65 ML Co/Ag-Si √3 × √3/Si(111) is between 275 and 300 K. while that of 3.51 ML Co/Ag-Si √3 × √3/Si(111) is below 150 K. In addition, my designs and efforts on the movement and reestablishment of the ultrahigh vacuum system have been discussed.