Teich, Lisa: Hybrid molecular and spin dynamics simulations of ensembles of magnetic nanoparticles in viscous matrices. 2016
Inhalt
- Declaration of Authorship
- List of Figures
- Publications
- 1 Introduction
- 2 Magnetoresistive systems
- 2.1 Magnetic nanoparticles
- 2.1.1 Magnetic interactions
- 2.1.2 Geometric frustration
- 2.1.3 Magnetic properties of nanoparticle ensembles
- 2.2 Magnetoresistance and related effects
- 2.2.1 Giant magnetoresistance (GMR) effect
- 2.2.2 Interlayer exchange coupling
- 2.2.3 Granular GMR effect
- 2.3 Magnetoresistive sensor systems
- 3 Basic simulation methods
- 3.1 Classical spin dynamics
- 3.1.1 Magnetic macro moment approximation
- 3.1.2 Classical equations of motion for the spin Hamiltonian
- 3.1.3 Landau-Lifshitz equation
- 3.1.4 Heat bath coupling
- 3.1.5 Integration of the spin equations of motion
- 3.1.6 Classical spin dynamics summary
- 3.2 Classical molecular dynamics
- 3.2.1 Potential energy functions
- 3.2.2 Particle-particle and particle-matrix interactions in systems of interacting magnetic particles in viscous surrounding media
- 3.2.3 Force calculation
- 3.2.4 Integration of the translational equations of motion
- 3.2.5 Molecular dynamics at constant temperature
- 3.2.6 Classical molecular dynamics summary
- 3.2.7 Reduced Lennard-Jones Units
- 4 Design of model systems
- 4.1 Experimental systems
- 4.2 3D reconstruction of nanoparticle ensembles
- 4.3 Structure determination by abstraction and downsizing
- 4.4 Design of model systems summary
- 5 Efficient calculation of magnetic low energy configurations of nanoparticle ensembles
- 5.1 Basic relaxation simulations
- 5.2 Demagnetization protocol
- 5.3 Comparison of simple relaxation and demagnetization protocol
- 5.4 Demagnetization simulations summary
- 6 Hybrid molecular and spin dynamics simulations
- 6.1 Motivation
- 6.2 Separation of the magnetic and mechanical degrees of freedom
- 6.2.1 Mechanical relaxation of magnetic particles in a viscous matrix
- 6.2.2 Magnetic relaxation
- 6.2.3 Comparison of mechanical and magnetic relaxation times
- 6.3 The role of temperature
- 6.4 Hybrid simulation coupling procedure
- 6.5 Validation: Hybrid simulation of a particle ring
- 6.6 Hybrid molecular and spin dynamics summary
- 7 Hybrid simulation of the model structure AH41 and estimation of its GMR properties
- 7.1 Hybrid simulation of AH41
- 7.2 Prediction of qualitative GMR properties
- 7.3 Hybrid simulation and evaluation of GMR curve of AH41 summary
- 8 Suggestions for further experimental investigations
- 8.1 Identification of promising configurations for the development of magnetoresistive sensor devices
- 8.2 Investigation of three-dimensional structures
- 8.3 Printed containers for magnetic spheres
- 8.4 Particle positioning via DNA-functionalization
- 8.5 Encapsulation of magnetic particles in liquid metals
- 8.6 Suggestions for further experimental investigations summary
- 9 Conclusion and outlook
- A Hybrid molecular and spin dynamics program description
- A.1 Input files
- A.2 Output files
- A.3 Modifications to the spin dynamics algorithm
- A.4 Modifications to HOOMD-blue
- Bibliography
- Danksagung