Giant magnetoresistance (GMR)

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Table of contents

1 Basics of magnetism and spin transfer torque 
1.1 Magnetic moment and magnetic interactions
1.1.1 Magnetic moment
1.1.2 Itinerant vs localized magnetism
1.1.2.1 Transition metals (TM)- model of itinerant magnetism
1.1.2.2 Magnetism of rare earth elements(RE) – model of localized electrons
1.1.3 Magnetic interactions
1.1.3.1 Zeeman energy
1.1.3.2 Exchange interaction
1.1.3.3 Dipolar energy and shape anisotropy
1.1.3.4 Magnetocrystalline anisotropy (MCA)
1.1.4 MCA of rare earth elements and MCA of transition metals .
1.1.5 Anisotropy of thin films
1.1.6 Magnetic domains and domain walls (DW)
1.2 Magnetoresistance
1.2.1 Anisotropic magnetoresistance (AMR)
1.2.2 Giant magnetoresistance (GMR)
1.2.3 Extraordinary Hall effect (EHE)
1.3 Magnetization reversal
1.3.1 Stoner Wohlfarth model
1.3.2 Magnetization reversal in thin films
1.3.2.1 Nucleation process
1.3.2.2 Propagation process
1.3.3 Domain wall propagation in a nanowires under field
1.3.4 Propagation of a DW in a nanowire without pinning sites
1.3.5 Propagation of a DW in a nanowire considering pinning sites .
1.3.5.1 DW pinning sites in nanowires
1.3.5.2 The depinning process in nanowires
1.3.6 Conclusion for the choice of a material as a model system
1.4 Magnetization reversal induced by a spin-polarized current
1.4.1 Dynamic of a magnetic moment : LLGS equation
1.4.2 Current-induced magnetization reversal and steady states precession in nanopillars
1.4.3 Current-induced DW propagation
1.5 Materials for spin torque experiments
1.5.1 In-plane vs out-of-plane materials
1.5.2 Materials used for experiments on spin transfer torque switching in nanopillars
1.5.3 Materials used for experiments on spin current driven domain wall propagation
1.6 Outline for the following manuscript
2 Les alliages de Co1−xTbx 51
2 CoTb-based alloys 
2.1 Growth and Structure
2.1.1 Sample preparation by DC magnetron sputtering
2.1.2 Structural analysis by transmission electron microscopy (TEM)
2.2 Magnetic properties
2.2.1 Magnetic structure of rare earth(RE) – transition metal(TM) alloys
2.2.2 Magnetization of the CoTb system
2.2.3 Perpendicular anisotropy in CoTb alloys
2.2.4 Magnetism of CoTb alloys as a function of layer thickness
2.2.5 Further data
2.2.5.1 Soft-magnetic contribution to hysteresis loops
2.2.5.2 Effects of annealing
2.2.6 Models describing the origin of PMA in RE-TM alloys
2.2.7 Conclusion on the magnetic properties of CoTb alloys
2.3 Magnetization reversal in Co1−xTbx alloys and Co1−xTbx-based spin valves
2.3.1 Reversal process of CoTb films
2.3.1.1 Domain pattern of CoTb films during reversal
2.3.1.2 Barkhausen length lB of the reversal process
2.3.1.3 Conclusion on the reversal process
2.3.2 Dipolar coupling in CoTb-based spin valves
2.3.2.1 Magnetometry results
2.3.2.2 Analysis by MFM imaging
2.3.2.3 Modelization of the dipolar field
2.3.2.4 Modification of the nucleation field
2.3.2.5 Conclusion
2.3.3 Conclusion on magnetization reversal in Co1−xTbx alloys and Co1−xTbx-based spin valves
2.4 Transport properties of CoTb alloys
2.4.1 Magnetoresistance of a Co88Tb12 layer
2.4.2 Magnetoresistance of CoTb-based spin valves
2.4.3 Temperature dependence of magnetoresistance
2.4.4 Angular dependence of magnetoresistance in CoTb alloys
2.4.5 Conclusion on the magnetoresistance of CoTb alloys
2.5 All-Optical magnetization switching in Co1−xTbx alloys
2.5.1 Mechanisms of all-optical magnetization switching
2.5.2 First results obtained for Co1−xTbx alloys
2.5.3 Conclusion and new perspectives
2.6 Conclusion and perspectives for CoTb alloys
3 Les super-r´eseaux [Co/Ni](111) ´epitaxi´es 
3 Epitaxial [Co/Ni](111) superlattices 101
3.1 Growth and structure of epitaxial [Co/Ni] films
3.1.1 Growth of [Co/Ni](111) superlattices
3.1.1.1 Al2O3 (1120) substrate
3.1.1.2 Growth of V(110)on Al2O3 (1120)
3.1.1.3 Growth of Au(111) on V(110)
3.1.1.4 Growth of [Co/Ni](111) superlattices on Au(111)
3.1.1.5 Conclusion on the growth of [Co/Ni](111) superlattices by molecular beam epitaxy
3.1.2 Ex-situ analysis of the sample structure
3.1.2.1 Verification of the atomic stacking by transmission electron microscopy (TEM)
3.1.2.2 Exact determination of lattice parameters
3.1.3 Conclusion on growth and structure of epitaxial [Co/Ni] films .
3.2 Magnetic properties of epitaxial [Co/Ni] superlattices
3.2.1 Part 1: Macroscopic magnetic properties
3.2.1.1 Hysteresis loops
3.2.1.2 Magnetization
3.2.1.3 Coercivity and saturation fields 3.2.1.4 Simple model explaining the perpendicular anisotropy
of [Co/Ni] superlattices
3.2.1.5 In-plane anisotropy of [Co/Ni] superlattices
3.2.2 Part 2: Microscopic magnetic properties
3.2.2.1 Details on the experiment and the treatment of XMCD data
3.2.2.2 XAS results
3.2.2.3 Determination of the magnetic moment by XMCD .
3.2.2.4 Conclusion on XMCD
3.2.3 Part 3: Dynamic magnetic properties
3.2.4 Conclusion on the magnetic properties of [Co/Ni] superlattices
3.3 Fully epitaxial spin valves based on [Co/Ni](111) superlattices
3.3.1 Growth and magnetic properties
3.3.2 Spin-resolved photoemission
3.3.2.1 Basics of spin-resolved photoemission
3.3.2.2 Experimental results for [Co/Ni] superlattices
3.3.3 Transport properties of [Co/Ni]/Au/[Co/Ni] spin valves
3.3.4 Conclusion on [Co/Ni]-based spin valve systems
3.4 Magnetization reversal of [Co/Ni] nanowires
3.4.1 Magnetization reversal in patterned [Co/Ni] layers
3.4.2 Propagation of domain walls in [Co/Ni] nanowires
3.4.3 Conclusion on the DW propagation in [Co/Ni] nanowires
3.5 Conclusions and perspectives for epitaxial [Co/Ni] superlattices
4 Conclusion 
References