This book presents relevant issues for the development of computer technology in general and civil aviation in particular, related to the promising task of developing magnetoresistive memory. In modern conditions of constantly increasing air traffic intensity, it is necessary to use both on board the aircraft and in ground services computing devices that guarantee the required level of flight safety. The book shows that in the multilayer ferromagnet-antiferromagnet system, the behavior of magnetic parameters in layers of nanometer thickness is largely determined by frustrations. The monograph provides not only a complete analysis of the current state of magnetic nanostructures but also predicts new types generated by exchange interaction frustrations. The phase diagrams "layer thickness (layers)―roughness" of a thin ferromagnetic film on an antiferromagnetic substrate and a spin-valve system ferromagnet-antiferromagnet-ferromagnet are constructed taking into account the energy of single-ion anisotropy. The book presents experimental results that confirm the existence of a new type of domain walls. It is shown that the detected domain walls appear exactly at the locations of the atomic steps, and their thickness increases in proportion to the film thickness with a proportionality coefficient of the order of one. Special attention using mathematical models is placed for optimal orientation of spins at a smooth interface in the case of a compensated cross section of an antiferromagnet and an uncompensated cross section. The constructed phase diagrams and models are compared with the experiments. It is thus concluded that scanning tunneling microscopy (STM) makes it possible to study domain walls generated by frustration on the surface of the structure.
Author(s): Alexander S. Sigov
Series: Springer Aerospace Technology
Publisher: Springer
Year: 2023
Language: English
Pages: 146
City: Singapore
Introduction
Contents
About the Author
Abbreviations
1 Physical Foundations for the Formation of Magnetic Nanostructures
1.1 The Phenomenon of Giant Magnetoresistance
1.2 GMR Theory
1.3 Tunnel Magnetoresistance
1.4 Spin-Polarized Current
1.5 MRAM (Magnetoresistive Random Access Memory)
1.6 Superparamagnetic Limit
References
2 Frustrations of Exchange Interaction
2.1 Why Does Spin Feel Hopeless?
2.2 Frustrations in a System with a Non-magnetic Layer
2.3 Frustrations in the Ferromagnet–Antiferromagnet System
2.3.1 Uncompensated Cross-Section of the Antiferromagnet Surface
2.3.2 Compensated Cross-Section of the Antiferromagnet Surface
References
3 Domain Walls and the Phase Diagram of the Spin-Valve Systems with a Non-magnetic Layer
3.1 Domain Wall Generated by Frustration
3.2 Phase Diagram
3.3 Behavior in a Magnetic Field
3.4 Experimental Observations
References
4 A Thin Film of a Ferromagnet on an Antiferromagnetic Substrate: Uncompensated Slice
4.1 Model Description
4.2 Solitary Domain Wall
4.2.1 γaf >>1
4.2.2 γaf <<1
4.3 Spin Vortices
4.4 Phase Diagram
4.5 Experimental Results
References
5 Compensated Slice
5.1 Spin-flop Orientation
5.2 The Case of “Charged” Edges of Atomic Steps at the Interface “Ferromagnet–Antiferromagnet”
5.2.1 Case of Weak Roughness
5.2.2 A Case of Strong Roughness. Thick Layer
5.2.3 A Case of Strong Roughness. Thin Layer
References
6 Behavior in a Magnetic Field
6.1 Exchange Bias. Uncompensated Slice
6.2 Exchange Bias. Compensated Slice
6.3 A Substrate of Finite Thickness. “Switching” the Nanodomain State
6.3.1 The Area of Strong Fields
6.3.2 The Area of Medium Fields
6.3.3 Weak Field Area
6.3.4 The “Switching” Field
6.3.5 Going Beyond the Exchange Approximation
6.4 Exchange Bias Near the Neel Temperature
References
7 Spin-Valve Structure Ferromagnet–Antiferromagnet–Ferromagnet
7.1 Frustrations in a Three-Layer System
7.2 Domain Walls in a Three-Layer System
7.2.1 γf, af a/γaf ll1
7.2.2 γf, af a/γaf gg1
7.3 Phase Diagram
7.4 Phase Transition “Polydomain State—Monodomain State with Exchange Spirals” in the Antiferromagnetic Layer
7.4.1 Simulation Results
7.4.2 Analytical Model
7.5 Behavior of a Spin-Valve Structure in a Magnetic Field in the Region of Applicability of the Exchange Approximation
7.6 Comparison with the Experiment. Magnetic Phase Diagram of a Spin-Valve Structure with an Antiferromagnetic Oxide Layer
7.6.1 Phase Diagram
7.6.2 Comparison with the Experiment
References
8 Surface Spin-flop Transition in Antiferromagnet
8.1 Volume Spin-flop Transition
8.2 The Case of an Atomically Smooth Surface
8.3 Size Effects in a Plane-parallel Layer of an Antiferromagnet with Smooth Surfaces
8.3.1 Even Number of Atomic Planes
8.3.2 Odd Number of Atomic Planes
8.4 Semi-infinite Antiferromagnet with Uncompensated Rough Surface
8.5 Antiferromagnet Layer with an Uncompensated Rough Surfaces
8.5.1 Thin Layer
8.5.2 Thick Layer
8.6 Possibilities of Experimental Observation
References
Conclusion
