許仁華臺灣大學：物理研究所薛志龍Xue, Zhi-LongZhi-LongXue2007-11-262018-06-282007-11-262018-06-282006http://ntur.lib.ntu.edu.tw//handle/246246/54525Magnetic coupling between two ferromagnetic layers through a spacer layer (metal, semiconductor or insulating) has been extensively studied during last several years and still attracts a lot of attention. This interaction is ferromagnetic (FM) or antiferromagnetic (AFM) depending upon spacer material and spacer thickness. For example, the interaction oscillates between FM and AFM couplings with spacer thickness for a trilayer with the metal spacer. In spite of many theoretical and experimental works devoted to this problem the origin of interlayer coupling is still under discussion. The detailed investigation of interlayer coupling as a function of temperature could provide a way to better understand the basic mechanisms involved on it; in this thesis, a series of CoFe (15 nm) / Bi (tBi) /Co (15 nm) sandwiches with tBi ranging from 1 to 56nm was prepared by dc sputtering to study the detailed temperature behavior of the interlayer exchange coupling. We performed measurements of the interlayer coupling as a function of the spacer thickness in the temperature range between 4K and 300K. It is observed that the FM coupling is persist when the temperature is decreased from 300K down to 4K whereas the AFM coupling switches to the FM coupling at low temperatures. The origin of this anomalous interlayer coupling with a Bi spacer as well as its temperature dependence is discussed in this thesis.CHAPTER 1 INTRODUCTION 1 CHAPTER 2 RELATED KNOWLEDGE 13 2.1. THEORY OF INTERLAYER EXCHANGE COUPLING 13 2.1.1. Bilinear coupling 13 2.1.1.1. RKKY coupling model 13 2.1.1.2. Quantum well model 14 2.1.2. Biquadratic coupling 15 2.1.2.1. Rough interface model 15 2.1.2.2. Loose spin model 17 2.1.2.3. Magnetic proximity effect 18 2.1.3. Temperature dependence of interlayer exchange coupling 19 2.1.3.1. Spacer contribution 19 2.1.3.2. Interface contribution 20 2.1.4. Experiments techniques 22 2.1.4.1. Static magnetometry 22 2.1.4.2. Domain observation 24 2.1.4.3. Spin waves monitoring 25 2.2. THE CHARACTERISTICS OF BISMUTH 26 2.2.1. Structure 26 2.2.2. Electronic Structure 28 2.2.3. Quantum Size effect of Bismuth 30 CHAPTER 3 EXPERIMENTAL 33 3.1. SAMPLE FABRICATION 33 3.1.1. HV Sputtering System 34 3.1.2. The Sputtering process 34 3.2. SAMPLE CHARACTERIZATION 37 3.2.1. Measurement of Film Thickness 37 3.2.2. Fabrication and Characterization of Cross-section TEM Samples 40 3.2.3. Determination of Crystalline Structures 42 3.2.4. Measurements of Magnetic Properties 47 3.2.4.1. Vibrating sample magnetometer (VSM) 47 3.2.4.2. Superconducting Quantum Interference Device (SQUID) 49 CHAPTER 4 RESULTS AND DISCUSSION 60 4.1. STRUCTURAL CHARACTERIZATION 60 4.1.1. Crystalline phase 60 4.1.2. Microstructure 60 4.2. MAGNETIC PROPERTY 61 4.2.1. Room Temperature behavior 61 4.2.2. Temperature dependence behavior 65 CHAPTER 5 CONCLUSION 70 5.1. ROOM TEMPERATURE BEHAVIOR 70 5.2. TEMPERATURE DEPENDENCE BEHAVIOR 70 BIBLIOGRAPHY 711696143 bytesapplication/pdfen-US層間交換耦合準金屬interlayer exchange couplingsemimetalthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/54525/1/ntu-95-R91222043-1.pdf