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Author: Andres Cornel Chavez Publisher: ISBN: Category : Languages : en Pages : 109
Book Description
In this work, voltage control of magnetism in nanoscale artificial multiferroic structures was demonstrated through numerical simulation and measurement. The multiferroic nanostructures studied in this dissertation were modeled using two methods. The first approach relies solely on the Landau-Lifshitz-Gilbert (LLG) equation and incorporates the effects of strain through an effective magnetic field term that only accounts for spatially-uniform strain distributions. The second-modeling technique couples the LLG equation with the elastodynamics and piezoelectric constitutive equations by using an innovative weak-formulation. In contrast to the purely micromagnetic model, the coupled solution can account for nonuniform distributions of strain and magnetization within nanostructures. Here, these simulation tools were used to understand the effects of strain on magnetoelastic nanodots and to investigate new coupling phenomena. Regarding strain effects, the innovative magnetic measurement technique of Scanning Electron Microscopy with Polarization Analysis (SEMPA) was used to observe strain-induced changes from vortex to antiparallel bidomain states in submicron Ni disks. This data was then used to validate the modeling methods of this dissertation. Consequently, the SEMPA study represents an advancement in terms of magnetic characterization and experimental model validation. Following this work, a design that leverages shape anisotropy, magnetic dipole coupling, and strain effects to achieve transitions between artificial antiferromagnetic and artificial ferromagnetic ordering is presented. Specifically, the micromagnetic models demonstrate voltage-induced transitions between these artificial magnetic states, but there are discrepancies with the measured data. To account for this, geometric defects are added to the models, thus dramatically improving the correlation between experiment and simulation. Importantly, this specific study demonstrates novel device behavior and introduces a modeling method to account for fabrication defects. Next, full 360i deterministic magnetization switching was numerically demonstrated with a design that consists of three dipole-coupled magnetoelastic ellipses patterned on a piezoelectric substrate. In comparison to other deterministic magnetization switching methods, this design reduces the complexity of electrical control and is more easily fabricated. Lastly, a novel design integrating multiferroics with artificial spin ices (ASI) is presented and used to provide the first numerical demonstration of local voltage-control of magnetic monopoles.
Author: Andres Cornel Chavez Publisher: ISBN: Category : Languages : en Pages : 109
Book Description
In this work, voltage control of magnetism in nanoscale artificial multiferroic structures was demonstrated through numerical simulation and measurement. The multiferroic nanostructures studied in this dissertation were modeled using two methods. The first approach relies solely on the Landau-Lifshitz-Gilbert (LLG) equation and incorporates the effects of strain through an effective magnetic field term that only accounts for spatially-uniform strain distributions. The second-modeling technique couples the LLG equation with the elastodynamics and piezoelectric constitutive equations by using an innovative weak-formulation. In contrast to the purely micromagnetic model, the coupled solution can account for nonuniform distributions of strain and magnetization within nanostructures. Here, these simulation tools were used to understand the effects of strain on magnetoelastic nanodots and to investigate new coupling phenomena. Regarding strain effects, the innovative magnetic measurement technique of Scanning Electron Microscopy with Polarization Analysis (SEMPA) was used to observe strain-induced changes from vortex to antiparallel bidomain states in submicron Ni disks. This data was then used to validate the modeling methods of this dissertation. Consequently, the SEMPA study represents an advancement in terms of magnetic characterization and experimental model validation. Following this work, a design that leverages shape anisotropy, magnetic dipole coupling, and strain effects to achieve transitions between artificial antiferromagnetic and artificial ferromagnetic ordering is presented. Specifically, the micromagnetic models demonstrate voltage-induced transitions between these artificial magnetic states, but there are discrepancies with the measured data. To account for this, geometric defects are added to the models, thus dramatically improving the correlation between experiment and simulation. Importantly, this specific study demonstrates novel device behavior and introduces a modeling method to account for fabrication defects. Next, full 360i deterministic magnetization switching was numerically demonstrated with a design that consists of three dipole-coupled magnetoelastic ellipses patterned on a piezoelectric substrate. In comparison to other deterministic magnetization switching methods, this design reduces the complexity of electrical control and is more easily fabricated. Lastly, a novel design integrating multiferroics with artificial spin ices (ASI) is presented and used to provide the first numerical demonstration of local voltage-control of magnetic monopoles.
Author: Mirko Ribow Publisher: ISBN: Category : Languages : en Pages :
Book Description
Voltage control of magnetic anisotropy; magnetic anisotropy; epitaxial growth; magnetism; spintronics; magneto optic Kerr-effect; ferromagnetic resonance; ultrathin magnetic layers; molecular beam epitaxy; microfabrication
Author: Ziyao Zhou Publisher: ISBN: Category : Electromagnetism Languages : en Pages : 129
Book Description
In past decades, attracted by the increasing demand of compact, fast, and low energy consumption RF/microwave devices, many researchers have devoted their efforts to realizing electric field control of magnetism, instead of magnetic field. For instance, within traditional RF/microwave devices, ferromagnetic resonance are controlled by bulky, noisy, slow and energy consumption electromagnets. This limits its application in many important, low mass and energy consuming requirement carriers, such as aircraft, satellites, radars and communication devices. As a result, novel functional material, which can be integrated into non-volatile, light, and energy-efficient electronic devices, need to be discovered. Multiferroics, a composite material combined with ferromagnetic material and ferroelectric material, is widely studied as a great candidate for E-field tunable RF/microwave applications like tunable resonators, phase shifters, tunable inductors and tunable filters. The coexistence of ferroelectricity and ferromagnetism in multiferroics introduces interaction between ferroelectric property and ferromagnetic properties, therefore, allowing electric field (E-field) control of ferromagnetism through varying mechanism. In our work, different mechanism-based magnetoelectric (ME) coupling in multiferroics heterostructure was investigated for the development of novel generation, voltage-controllable, high-speed, compact RF/microwave devices with greater energy efficiency. irstly, ME coupling was realized in different magnetic thin film/ferroelectric slab heterostructures. By decreasing the saturation magnetization of Cr doping Ni magnetic thin film, large ME coupling in NiCr/PbZr0.52Ti0.48O3 (PZT) and NiCr/PbZn1/3Nb2/3O2.4(PbTiO3)0.6 (PZNPT) was obtained. Furthermore, non-volatile voltage impulse tunability was discovered through electric field-induced phase transition in FeGaB/PZNPT multiferroics heterostructure. Giant ME coupling coefficient ~3000 Oe cm/kV was observed at PZNPT phase transition points. In FeGaB/Pb0.8Sn0.2Zr0.52Ti0.48O3 (PSZT) magnetic/antiferroelectric multiferroic heterostructure, antiferroelectric-ferroelectric phase transition in PSZT substrate gives us another opportunity to realize the voltage impulse tunable magnetic properties. The non-volatile tunability with large ME coupling effect offers a great opportunity of E-field control of magnetism in real RF/microwave applications. Secondly, traditional deposition methods like sputtering, Pulsed laser deposition (PLD), or Molecular beam epitaxy (MBE) require a high fabrication temperature (>600 oC), which limits their application in integrated circuits. We used low temperature(oC) spin spray method to deposit ZnO thin film with good electric, optical and piezoelectric performance. Fe3O4/ZnO bilayer heterostructure was also deposited by spin spray method. Significant ME coupling effective field of 14 Oe was observed by ferromagnetic resonance (FMR) measurements, paved a way to the application of multiferroics heterostructure in real industry. Finally, in real RF/microwave ME devices, magnetic thin film/ferroelectric slab heterostructure requires a higher voltage(~600 V) to tune the magnetic properties, therefore restraining their application. Nevertheless, strain/stress mediated ME coupling in thin films heterostructure is limited by sample clamping effect. Therefore other mechanisms-induced ME coupling were also studied in our experiment. Large interfacial charge mediated ME coupling effective field of 40 Oe was achieved in Co0.3Fe0.7/Ba0.6Sr0.4TiO3 multiferroic heterostructure. The charge effect amplitude dependence of magnetic film thickness was systematically investigated in NiFe/SrTiO3 multiferroic heterostructure. Lastly, the ME coupling in CoFe/BiFeO3 (BFO) heterostructure induced by interfacial exchange coupling between CoFe moment and canted moment in BFO was studied quantitively by FMR measurements.
Author: Mirza I. Bichurin Publisher: CRC Press ISBN: 0429949618 Category : Science Languages : en Pages : 280
Book Description
This book is dedicated to modeling and application of magnetoelectric (ME) effects in layered and bulk composites based on magnetostrictive and piezoelectric materials. Currently, numerous theoretical and experimental studies on ME composites are available but few on the development and research of instruments based on them. So far, only investigation of ME magnetic field sensors has been cited in the existing literature. However, these studies have finally resulted in the creation of low-frequency ME magnetic field sensors with parameters substantially exceeding the characteristics of Hall sensors. The book presents the authors’ many years of experience gained in ME composites and through creation of device models based on their studies. It describes low-frequency ME devices, such as current and position sensors and energy harvesters, and microwave ME devices, such as antennas, attenuators, filters, gyrators, and phase shifters.
Author: Sen Zhang Publisher: Springer Science & Business Media ISBN: 3642548393 Category : Science Languages : en Pages : 143
Book Description
This book mainly focuses on the investigation of the electric-field control of magnetism and spin-dependent transportation based on a Co40Fe40B20(CoFeB)/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) multiferroic heterostructure. Methods of characterization and analysis of the multiferroic properties with in situ electric fields are induced to detect the direct magnetoelectric (ME) coupling. A switchable and non-volatile electric field control of magnetization in CoFeB/PMN-PT(001) structures is observed at room temperature, and the mechanism of direct coupling between the ferroelectric domain and ferromagnetic film due to the combined action of 109° ferroelastic domain switching in PMN-PT and the absence of magnetocrystalline anisotropy in CoFeB is demonstrated. Moreover, the electric-field control of giant magnetoresistance is achieved in a CoFeB-based spin valve deposited on top of (011) oriented PMN-PT, which offers an avenue for implementing electric-writing and magnetic-reading random access memory at room temperature. Readers will learn the basic properties of multiferroic materials, many useful techniques related to characterizing multiferroics and the interesting ME effect in CoFeB/PMN-PT structures, which is significant for applications.
Author: Hervé Bulou Publisher: Springer Nature ISBN: 3030646238 Category : Science Languages : en Pages : 208
Book Description
This open access book collects the contributions of the seventh school on Magnetism and Synchrotron Radiation held in Mittelwihr, France, from 7 to 12 October 2018. It starts with an introduction to the physics of modern X-ray sources followed by a general overview of magnetism. Next, light / matter interaction in the X-ray range is covered with emphasis on different types of angular dependence of X-ray absorption spectroscopy and scattering. In the end, two domains where synchrotron radiation-based techniques led to new insights in condensed matter physics, namely spintronics and superconductivity, are discussed. The book is intended for advanced students and researchers to get acquaintance with the basic knowledge of X-ray light sources and to step into synchrotron-based techniques for magnetic studies in condensed matter physics or chemistry.
Author: Evgeny Y. Tsymbal Publisher: CRC Press ISBN: 0429750889 Category : Science Languages : en Pages : 670
Book Description
Spintronics Handbook, Second Edition offers an update on the single most comprehensive survey of the two intertwined fields of spintronics and magnetism, covering the diverse array of materials and structures, including silicon, organic semiconductors, carbon nanotubes, graphene, and engineered nanostructures. It focuses on seminal pioneering work, together with the latest in cutting-edge advances, notably extended discussion of two-dimensional materials beyond graphene, topological insulators, skyrmions, and molecular spintronics. The main sections cover physical phenomena, spin-dependent tunneling, control of spin and magnetism in semiconductors, and spin-based applications.
Author: Miguel Alguero Publisher: John Wiley & Sons ISBN: 1118935705 Category : Technology & Engineering Languages : en Pages : 984
Book Description
This two volume set reviews the key issues in processing and characterization of nanoscale ferroelectrics and multiferroics, and provides a comprehensive description of their properties, with an emphasis in differentiating size effects of extrinsic ones like boundary or interface effects. Recently described nanoscale novel phenomena are also addressed. Organized into three parts it addresses key issues in processing (nanostructuring), characterization (of the nanostructured materials) and nanoscale effects. Taking full advantage of the synergies between nanoscale ferroelectrics and multiferroics, the text covers materials nanostructured at all levels, from ceramic technologies like ferroelectric nanopowders, bulk nanostructured ceramics and thick films, and magnetoelectric nanocomposites, to thin films, either polycrystalline layer heterostructures or epitaxial systems, and to nanoscale free standing objects with specific geometries, such as nanowires and tubes at different levels of development. This set is developed from the high level European scientific knowledge platform built within the COST (European Cooperation in Science and Technology) Action on Single and multiphase ferroics and multiferroics with restricted geometries (SIMUFER, ref. MP0904). Chapter contributors have been carefully selected, and have all made major contributions to knowledge of the respective topics, and overall, they are among most respected scientists in the field.
Author: Kevin O'Grady Publisher: Oxford University Press ISBN: 0192873121 Category : Science Languages : en Pages : 256
Book Description
Aimed primarily at experimental chemists, physicists, electronic engineers and material scientists interested in particulate and granular magnetic materials, this textbook is the culmination of over 40 years' research into the subject. The text is divided into two parts. Part One covers the basic physics of magnetism from a relatively low level, including an explanation of some of the unusual terminology in magnetism such as the idea of poles and flux, whose origins are little understood. The complexity of the unit systems in magnetism are also presented. Thereafter a brief review of the principles of domain theory is presented and thermal activation effects and their correct measurement are discussed in some detail. The topic of exchange bias, where an antiferromagnetic material is grown in intimate contact with a ferromagnet, is presented in significant detail reviewing old theories and numerical models but then focusing on what has become known as the York Model of Exchange Bias which is now universally accepted as the model which describes the behaviour of exchange bias systems when grown in the form of granular thin films. In Part Two a detailed description of ferrofluids is presented including a simple method for their preparation and the various engineering applications in vacuum seals, loudspeakers, sink float separation and the alignment of non-magnetic entities.A description is provided of the phenomenon of magnetic hyperthermia which is a developing technology with significant potential applications in medicinal therapies. Other applications of magnetic nanoparticles in biomedicine are also presented. An extensive discussion of magnetic information storage in conventional recording systems is described, including the brief history of the development of this technology whose scale is now enormous as most of the cloud computing systems in current use are based on hard drive technology.
Author: Ram K. Gupta Publisher: CRC Press ISBN: 1000640264 Category : Science Languages : en Pages : 480
Book Description
A low-dimensional magnet is a key to the next generation of electronic devices. In some respects, low-dimensional magnets refer to nanomagnets (nanostructured magnets) or single-molecule magnets (molecular nanomagnets). They also include the group of magnetic nanoparticles, which have been widely used in biomedicine, technology, industries, and environmental remediation. Low-dimensional magnetic materials can be used effectively in the future in powerful computers (hard drives, magnetic random-access memory, ultra-low power consumption switches, etc.). The properties of these materials largely depend on the doping level, phase, defects, and morphology. This book covers various nanomagnets and magnetic materials. The basic concepts, various synthetic approaches, characterizations, and mathematical understanding of nanomaterials are provided. Some fundamental applications of 1D, 2D, and 3D materials are covered. This book provides the fundamentals of low-dimensional magnets along with synthesis, theories, structure-property relations, and applications of ferromagnetic nanomaterials. This book broadens our fundamental understanding of ferromagnetism and mechanisms for realization and advancement in devices with improved energy efficiency and high storage capacity.
Author: Andres Cornel Chavez
Author: Andres Cornel Chavez
Author: Mirko Ribow
Author: Ziyao Zhou
Author: Mirza I. Bichurin
Author: Sen Zhang
Author: Hervé Bulou
Author: Evgeny Y. Tsymbal
Author: Miguel Alguero
Author: Kevin O'Grady
Author: Ram K. Gupta