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Table of contents
Chapter 1: Sm1-xGdxAl2, a recent story
I. From Sm3+ to SmAl2
I.A. Localized magnetism in Lanthanide metals
I.B. Sm multiplets mixing in a metallic matrix
I.C. SmAl2, a self-ferrimagnet
II. Sm1-xGdxAl2, a zero-magnetization ferromagnet
II.A. First evidence of the zero-magnetization state
II.B. Ferromagnetic order at Tcomp
III. SGA as epitaxial films
III.A. Epitaxial growth and structural properties
III.B. Magnetic properties
III.B.1. Perpendicular anisotropy and giant coercivity
III.B.2. 5d spin polarization and long-range ferromagnetic order
IV. SGA epitaxial films in magnetic heterostructures
IV.A. Exchange-coupled bilayers
IV.B. Magnetic Tunnel Junctions
V. Summary and purpose of this thesis
References
Chapter 2: Photoemission spectroscopy
I. Generalities on photoemission spectroscopy
I.A. Photoemission and the photoelectric effect
I.B. The three-steps model
I.B.1. Optical excitation of one electron in the solid
I.B.2. Propagation of the photoelectron to the surface
I.B.3. Escape of the photoelectron from the solid to the vacuum
I.C. Photoemission and dipole selection rules
II. Angle Resolved PhotoEmission Spectroscopy (ARPES)
II.A. Geometry of the ARPES experiment
II.B. Information provided by ARPES experiments
III. Spin-Resolved PhotoEmission Spectroscopy
IV. CASSIOPEE beamline
V. Conclusion
References
Chapter 3: Electronic properties of (111)Sm1-xGdxAl2 surface and interface
I. Literature review
I.A. Electronic band structure in Rare Earth dialuminides
I.B. Valence stability in Sm metal and SmAl2
I.C. Electronic surface state in Lanthanide elements
II. (111) SGA surface preparation and characterization
II.A. Chemical analysis
II.B. Structural analysis of the Nb-free surface
II.C. Electronic analysis
III. Electronic structure of (111) SGA surface
III.A. Samarium 4f multiplets
III.B. Valence band analysis (ARPES)
III.B.1 In-plane wave vector measurements
III.B.2 Out-of-plane wave vector measurements
III.B.3 Discussion on the nature of observed electronic states
III.C. Spin Resolved analysis
IV. Electronic structure of (111)SGA/MgO
IV.A. Interface oxidation
IV.B. Samarium 4f multiplets
IV.C. Valence band analysis
V. Conclusion
References
Chapter 4: Overview of the magnetic anisotropy in [Co/Pt] multilayers
I. Introduction to the magnetic anisotropy
I.A. Origin of magnetic anisotropy in thin magnetic films
I.A.1. Shape anisotropy
I.A.2. Magneto-crystalline anisotropy
I.A.3. Surface or interface anisotropy
I.A.4. Magneto-elastic anisotropy
I.B. Effect of the roughness and interface alloy
I.C. Experimental determination of Keff
I.D. Stoner-Wohlfarth model
II. Perpendicular Magnetic Anisotropy in [Co/Pt] multilayers
II.A. Influence of the crystallographic orientation and preparations
II.B. Deviation from the linear behavior
III. Conclusion
References
Chapter 5: Magnetic and structural properties in [Co/Pt] multilayers
I. Description of the [Co/Pt] multilayers
II. Structural properties of the [Co/Pt] multilayers
II.A. Generalities on X-ray diffraction
II.B. Experimental setup
II.C. Growth direction in the sputtered [Co/Pt] multilayers
II.D. Reflectometry analysis on [Co/Pt] multilayers
II.D.1. Co and Pt thicknesses
II.D.2. Co and Pt roughnesses
III. Magnetic properties in the [Co/Pt] multilayers
III.A. Experimental setup
III.B. Experimental results
III.B.1 Effective anisotropy
III.B.2. Saturation magnetization
III.B.3. Influence of temperature
IV. Conclusion
References
Chapter 6: Magnetic Tunnel Junctions with [Co/Pt]-based electrodes
I. Introduction
I.A. MTJ’s structure
I.B. Micromagnetic simulations and magnetic parameters of the materials
II. Magnetic properties in MTJs full stack
II.A. Magnetization reversal
II.B. Magnetic configurations
II.B.1. Influence of the applied magnetic field
II.B.2. Influence of the temperature
II.B.3. Calculated (H,T) phase diagram for the hard electrode
III. Transport properties in nano-patterned MTJs
III.A. Common features in perpendicular MTJs
III.A.1. Tunnel characteristics
III.A.2. R(H) characteristics
III.B. Phase diagrams in nano-patterned MTJs
III.B.1. Duplication of domains from the hard to the soft electrode
III.B.2. Spring magnet and exchange bias behavior
III.C. Coupling through the MgO barrier
IV. Conclusion
References
Chapter 7: Spin-polarization in [Co/Pt]- and SGA- based magnetic tunnel junctions
I. TMR and effective polarization in [Co/Pt] based-MTJs
I.A. Effective polarization of [Co/Pt]: more than an interface phenomenon?
I.B. Bloch low and Curie temperature
II. TMR and spin-polarization in SGA/AlOx/[Co/Pt] MTJs
II.A. Tunnel characteristic
II.B. Finite magneto-resistance tunnel at the magnetic compensation
II.C. Discussion
III. Preliminary results on SGA/MgO/[Co/Pt] MTJs
III.A. SGA surface preparation
III.B. Common features in perpendicular SGA-based MTJs
III.B.1. Tunnel conductance versus voltage
III.B.2. Tunnel conductance versus temperature
III.B.3. Resistance versus applied field characteristics
III.C. Discussion
IV. Conclusion
References
