Nowadays perpendicular ferromagnetic nanowires have drawn substantial interest because of the potential use in many areas of advanced nanotechnology, particularly high-density recording media. A great recording medium in this respect includes a densely organized assembly of nanometer-scale ferromagnets with high magnetization and suitable coercivity. In this report a novel and straightforward technique to create self-assembled nanowires of a-Fe through the decomposition of a suitably chosen perovskite is reported. We demonstrate the principle behind this method using the reaction 2La0.5Sr0.5FeO3 ? LaSrFeO4 + Fe + O2 that occurs during the deposition of La0.5Sr0.5FeO3 under reducing conditions. This results in the spontaneous formation of an array of single crystalline a-Fe nanowires embedded in LaSrFeO4 matrix, which grow perpendicular…….
Contents
Chapter 1 Introduction
1.1 Magnetic nanostructures
1.2 Ferromagnetic nanowires
1.3 Present approach: self-assembly of ferromagnetic nanowires
1.3.1 Reduction of perovskite LaMO3
1.3.1.1 Introduction
1.3.1.2 Properties of the LaSrFeO3 perovskite
1.3.2 Three-dimensional heteroepitaxy in thin film growth
1.4 Applications of self-assembled iron nanowires
1.4.1 Perpendicular recording media
1.4.2 Compact tunable microwave oscillators in magnetic nano-contact arrays
1.5 Outline of the dissertation
Chapter 2 Experimental Techniques
2.1 Pulsed laser deposition
2.2. Structural characterization
2.2.1. X-Ray diffraction
2.2.2 Transmission electron microscopy
2.3 Magnetic measurements
2.3.1 Mössbauer spectroscopy
2.3.2 Vibrating sample magnetometer
2.3.3 Superconducting quantum interference device Magnetometer
2.3.4 Magnetic force microscopy
Chapter 3 Self-Assembly of Ferromagnetic Iron Nanowires
3.1 Pulsed laser deposition of La0.5Sr0.5FeO3
3.2 Structure and properties of thin films
3.2.1 X-ray diffraction results
3.2.2 Transmission electron microscopy results
3.2.3 Energy dispersive X-ray spectroscopy results
3.2.4 Mössbauer spectroscopy results
3.3 Properties of nanowires and the matrix
3.4.1 Properties of α-Fe
3.3.2 Properties of LaSrFeO4 matrix
3.4 Calculation of α-Fe volume fraction
3.4.1 Theoretical calculation
3.4.2 Mössbauer spectroscopy
3.5 Controlling the density of α-Fe nanowires
3.6. Growth on silicon substrate
3.7 Annealing self-assembled α-Fe nanowires
Chapter 4 Shape and Size Evolution of the α-Fe Nanowires
4.1 Introduction
4.2 Temperature dependence of the lateral size of the iron nanowires
4.3 Lateral shape changes of the iron nanowires
4.3.1 Crystallographic symmetry and group theory
4.3.1.1 Symmetry of heterophase interfaces
4.3.1.2 Symmetry of α-Fe nanostructures embedded in LaSrFeO4 matrix
4.3.2 Shape evolution of coherent precipitates in elastic media
4.3.2.1 Theoretical calculations
4.3.2.2 Shape evolution of α-Fe nanostructures embedded in LaSrFeO4 matrix
Chapter 5 Magnetic Properties of Self-Assembled α-Fe Nanowires
5.1 Introduction
5.2 Theoretical framework for nanomagnets
5.3 Magnetic properties of self-assembled nanowires
5.4 Magnetic force microscopy of iron nanowires
Chapter 6 Growth of Carbon Nanotubes on α-Fe Nanowires
6.1 Definition and properties of carbon nanotubes
6.2 Synthesis of carbon nanotubes
6.2.1 Methods
6.2.1 Catalyst
6.2.3 Hydrogen
6.3 Growth mechanism of carbon nanotube
6.4 Catalytic plasma enhanced chemical vapor deposition
6.4.1 PECVD experimental system
6.4.2 CNT growth mechanism in PECVD
6.5 Vertically aligned CNTs and CNFs
6.6 Applications of carbon nanotubes
6.7 Carbon nanotubes grown on self-assembled iron nanowires……
Source: University of Maryland