Low-angle polarized neutron and X-ray scattering from magnetic nanolayers and nanostructures

149 Pages·2017·22.33 MB·English

by  Paul

Springer Tracts in Modern Physics 273
Amitesh Paul
Low-Angle Polarized
Neutron and X-Ray
Scattering from
Magnetic Nanolayers
and Nanostructures
Springer Tracts in Modern Physics
Volume 273
Series editors
Yan Chen, Department of Physics, Fudan University, Shanghai, China
Atsushi Fujimori, Department of Physics, University of Tokyo, Tokyo, Japan
Thomas Müller, Inst für Experimentelle Kernphysic, Universität Karlsruhe,
Karlsruhe, Germany
William C. Stwalley, Storrs, CT, USA
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Amitesh Paul
Low-Angle Polarized
Neutron and X-Ray
Scattering from Magnetic
Nanolayers
and Nanostructures
123
Amitesh Paul
Department ofPhysics
Technical University Munich
Garching
Germany
ISSN 0081-3869 ISSN 1615-0430 (electronic)
SpringerTracts inModern Physics
ISBN978-3-319-63223-0 ISBN978-3-319-63224-7 (eBook)
DOI 10.1007/978-3-319-63224-7
LibraryofCongressControlNumber:2017946662
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BTO BTO BTO
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For Angelika and Angelina, who wonder
what I did all the time.
In particular I express my enduring thanks
to my wife Neelima. Without her patience,
understanding, and love I could not have
completed this book.
Contents
1 Introduction.... .... .... ..... .... .... .... .... .... ..... .... 1
1.1 Polarized Neutron Reflectometry on Metallic Nanolayers
and Multilayers.. .... ..... .... .... .... .... .... ..... .... 2
1.2 Grazing Incidence Small Angle X-Ray Scattering
on Self–organized Metallic Nanostructures.. .... .... ..... .... 8
2 Low-Angle Scattering Theory and Techniques. .... .... ..... .... 13
2.1 Polarized Neutron Scattering .... .... .... .... .... ..... .... 13
2.1.1 Fundamentals in Neutron Scattering .... .... ..... .... 14
2.1.2 Refractive Index and Specular Reflection .... ..... .... 16
2.1.3 Polarized Neutron Specular Reflectivity . .... ..... .... 18
2.1.4 Resolution and Coherence Volume. .... .... ..... .... 23
2.1.5 Off-Specular Neutron Scattering ... .... .... ..... .... 28
2.2 Grazing Incidence Small Angle X-Ray Scattering .... ..... .... 36
3 Scattering Instruments ... ..... .... .... .... .... .... ..... .... 43
3.1 Neutron Reflectometer ..... .... .... .... .... .... ..... .... 43
3.1.1 Monochromator Instrument... .... .... .... ..... .... 43
3.1.2 TOF Instrument.... .... .... .... .... .... ..... .... 45
3.2 GISXAS Instruments . ..... .... .... .... .... .... ..... .... 47
4 Magnetic Nanolayers and Superlattices... .... .... .... ..... .... 49
4.1 Interlayer-Exchange Coupling.... .... .... .... .... ..... .... 49
4.1.1 Interlayer-Coupling Through Metallic Systems ..... .... 49
4.1.2 Oscillatory Nature and Non-collinear Coupling..... .... 52
4.1.3 Magnetic Domain Structure... .... .... .... ..... .... 53
4.1.4 Fermi Surface Topography ... .... .... .... ..... .... 54
4.1.5 Spin-Flop Phase ... .... .... .... .... .... ..... .... 54
4.1.6 Coupling of Heusler Alloys... .... .... .... ..... .... 55
4.1.7 Domain Structure Evolution with Number
of Bilayers... ..... .... .... .... .... .... ..... .... 55
ix
x Contents
4.1.8 Interlayer Coupling Through Semiconducting
Spacers . .... ..... .... .... .... .... .... ..... .... 59
4.1.9 Twisted State of Interface Magnetization. .... ..... .... 59
4.2 Dilute Magnetic Semiconductor .. .... .... .... .... ..... .... 61
4.2.1 Coupling of Superlattices .... .... .... .... ..... .... 63
4.2.2 Magnetic Ion Distribution.... .... .... .... ..... .... 64
4.2.3 Coupling of DMS via Doped Spacer.... .... ..... .... 64
4.2.4 Ge Based DMS: Homogeneity
and Inhomogeneity . .... .... .... .... .... ..... .... 64
4.3 Exchange Bias at Antiferromagnetic-Ferromagnetic Interfaces.... 67
4.3.1 Exchange Bias..... .... .... .... .... .... ..... .... 67
4.3.2 Correlation of Bias Field with the Number
of Uncompensated Spins in the AF and Increase
in Coercivity. ..... .... .... .... .... .... ..... .... 69
4.3.3 Asymmetric Magnetization Reversal.... .... ..... .... 69
4.3.4 Training Effect .... .... .... .... .... .... ..... .... 72
4.3.5 Exchange Coupled Double-Superlattice.. .... ..... .... 73
4.3.6 Depth Dependence of Magnetization.... .... ..... .... 74
4.3.7 Grain-Size Induced Exchange Bias . .... .... ..... .... 74
4.3.8 Mystery of Symmetry and Asymmetry in Reversal.. .... 77
4.3.9 Magnetization Reversal in Bilayer and Multilayer... .... 81
4.3.10 Field-Cooling and Training in Bilayer Units.. ..... .... 84
4.3.11 Change in Interface Magnetism Due to the Presence
of Nonmagnetic Spacers . .... .... .... .... ..... .... 88
4.3.12 Exchange Bias Manipulation by keV or GeV Ion
Irradiation ... ..... .... .... .... .... .... ..... .... 90
4.3.13 Recovery of the Untrained State ... .... .... ..... .... 93
4.4 Coupling in Multilayers with Non-collinear Spin Textures... .... 95
4.4.1 Rare-Earth/Ferromagnetic Multilayer.... .... ..... .... 95
4.4.2 Rare-Earth/Rare-Earth Multilayer .. .... .... ..... .... 99
5 Self-assembly of Nanolayers and Nanostructures ... .... ..... .... 103
5.1 Self-assembly of Nanolayers. .... .... .... .... .... ..... .... 103
5.1.1 Superparamagnetic Nanopillar-Like Structures ..... .... 104
5.1.2 Metal–Oxide Interfaces .. .... .... .... .... ..... .... 105
5.1.3 Oxide–Oxide Interfaces.. .... .... .... .... ..... .... 109
5.2 In Situ Growth Morphology. .... .... .... .... .... ..... .... 111
5.2.1 Au on Quantum Dot Template .... .... .... ..... .... 111
5.2.2 Fe-Pt Nanolayer Morphology Due to Low Temperature
Annealing ... ..... .... .... .... .... .... ..... .... 112
Contents xi
6 Magnetic Oxide Heterostructures and Their Interfaces: Proximity
and Coupling... .... .... ..... .... .... .... .... .... ..... .... 115
6.1 Ferroelectric–Ferromagnet Interfaces .. .... .... .... ..... .... 115
6.1.1 Enhanced Moment at the Interface . .... .... ..... .... 116
6.1.2 Vertical Shift Due to Exchange Coupling.... ..... .... 116
6.1.3 Exchange Coupling Due to Symmetry Mismatch ... .... 119
6.2 Superconductor–Ferromagnet Interfaces .... .... .... ..... .... 121
6.2.1 Superconductivity-Induced Magnetization Depletion. .... 121
7 Self-diffusion Kinetics in Layered Systems .... .... .... ..... .... 125
7.1 Self-diffusivity and the Effect of Grain Size. .... .... ..... .... 125
7.1.1 Ex Situ Self-diffusivity with Grain Size Variation... .... 126
7.1.2 In Situ Self-diffusivity... .... .... .... .... ..... .... 127
8 Summary and Outlook... ..... .... .... .... .... .... ..... .... 131
References.... .... .... .... ..... .... .... .... .... .... ..... .... 135