Investigations of Magnetic/electric Field Control of Magnetization of Ferromagnetic and Multiferroics PDF Download

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Category : Ferromagnetic materials
Languages : en
Pages : 0

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The shortcomings of contemporary complementary metal oxide semiconductor (CMOS) technologies include increased power consumption, scalability, volatility, and device variability. New materials and novel devices are being investigated in this regard. Spintronic devices, which are normally based on magnetic materials, store and process data based on the modes of electron spins, rather than the presence or absence of charges as in the CMOS, are one possible approach. Numerous potential advantages of spintronic devices include its quick operational speed, low power requirement, and non-volatility. Two ferromagnetic materials suitable for creating spintronic devices are investigated in this dissertation study. Material properties, techniques for regulating the magnetization of materials, with both magnetic and electrical fields, and the development of devices useful for use in frequency modulations are all respectively detailed. The first section of this dissertation studies the magnetically-induced transparence (MIT) effect in Y3Fe5O12 (YIG)/Permalloy (Py) coupled bilayers. The measurement is achieved via a heterodyne detection of the coupled magnetization dynamics using a single wavelength that probes the magneto-optical Kerr and Faraday effects of Py and YIG, respectively. Clear features of the MIT effect are evident from the deeply modulated ferromagnetic resonance of Py due to the perpendicular-standing-spin-wave of YIG. We develop a phenomenological model that nicely represents the experimental results including the induced amplitude and phase evolution caused by the magnon-magnon coupling. This work offers a new route towards studying phase-resolved spin dynamics and hybrid magnonic systems. The second part of this dissertation discusses the research on the hexaferrite material, Zn2Y, and the prospect of controlling its magnetic characteristics by applying a dc voltage, which is akin to a bias electric field. The detection and investigation of the magnetoelectric (ME) effect for in-plane currents orthogonal to the hexagonal axis in single crystal and thin films of Zn2Y grown via liquid phase epitaxy. By applying a dc voltage, tuning of ferromagnetic resonance (FMR) was achieved in the hexaferrites. In addition to the frequency shift caused by the electrical tuning, magnetic properties of the material as a function of the input tuning power was also studied.

Author: Sen Zhang
Publisher: Springer Science & Business Media
ISBN: 3642548393
Category : Science
Languages : en
Pages : 143

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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: John Thomas Heron
Publisher:
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Category :
Languages : en
Pages : 320

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This dissertation presents a study of a heterostructure composed of room temperature magnetoelectric multiferroic BiFeO3 and ferromagnetic Co90Fe10, with specific interest in understanding the interfacial coupling mechanisms in this system and establishing the electric field control of a magnetization and spintronic devices. The field of spintronics has been plagued with the problem of a large energy dissipation as a consequence of the resistive losses that come during the writing of the magnetic state (i.e. reversing the magnetization direction). The primary aim of the work presented here is to investigate and understand a novel heterostructure and materials interface that can be demonstrated as a pathway to low energy spintronics. In this dissertation, I will address the specific aspects of multiferroicity, magnetoelectricity, and interface coupling that must be addressed in order to reverse a magnetization with an electric field. Furthermore, I will demonstrate the reversal of a magnetization with an electric field in single and multilayer magnetic devices. The primary advances made as a result of the work described herein are the use of epitaxial constraints to control the nanoscale domain structure of a multiferroic which is then correlated to the domain structure of the exchange coupled ferromagnet. Additionally, the magnetization direction of the ferromagnetic layer is controlled with only an applied electric field at both macroscopic and microscopic scales. Lastly, using this electric field control of ferromagnetism, the first demonstration of a magnetoelectric memory bit is presented.

Author: Ziyao Zhou
Publisher:
ISBN:
Category : Electromagnetism
Languages : en
Pages : 129

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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: Weigang Yang
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Shinichiro Seki
Publisher: Springer Science & Business Media
ISBN: 4431540911
Category : Science
Languages : en
Pages : 135

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Electric control of magnetic properties, or inversely, magnetic control of dielectric properties in solids, is called a magnetoelectric effect and has long been investigated from the point of view of both fundamental physics and potential application. Magnetic and dielectric properties usually show minimal coupling, but it recently has been discovered that magnetically induced ferroelectricity in some spiral magnets enables remarkably large and versatile magnetoelectric responses. To stabilize such helimagnetism, magnetic frustration (competition between different magnetic interactions) is considered the key. In the present work, two of the most typical frustrated spin systems—triangular lattice antiferromagnets and edge-shared chain magnets—have systematically been investigated. Despite the crystallographic simplicity of target systems, rich magnetoelectric responses are ubiquitously observed. The current results published here offer a useful guideline in the search for new materials with unique magnetoelectric functions, and also provide an important basis for a deeper understanding of magnetoelectric phenomena in more complex systems.

Author: Jill Guyonnet
Publisher: Springer Science & Business Media
ISBN: 3319057502
Category : Science
Languages : en
Pages : 167

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Using the nano metric resolution of atomic force microscopy techniques, this work explores the rich fundamental physics and novel functionalities of domain walls in ferroelectric materials, the nano scale interfaces separating regions of differently oriented spontaneous polarization. Due to the local symmetry-breaking caused by the change in polarization, domain walls are found to possess an unexpected lateral piezoelectric response, even when this is symmetry-forbidden in the parent material. This has interesting potential applications in electromechanical devices based on ferroelectric domain patterning. Moreover, electrical conduction is shown to arise at domain walls in otherwise insulating lead zirconate titanate, the first such observation outside of multiferroic bismuth ferrite, due to the tendency of the walls to localize defects. The role of defects is then explored in the theoretical framework of disordered elastic interfaces possessing a characteristic roughness scaling and complex dynamic response. It is shown that the heterogeneous disorder landscape in ferroelectric thin films leads to a breakdown of the usual self-affine roughness, possibly related to strong pinning at individual defects. Finally, the roles of varying environmental conditions and defect densities in domain switching are explored and shown to be adequately modelled as a competition between screening effects and pinning.

Author: Miguel Alguero
Publisher: John Wiley & Sons
ISBN: 1118935705
Category : Technology & Engineering
Languages : en
Pages : 984

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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: Takayuki Kurihara
Publisher: Springer Nature
ISBN: 9811687935
Category : Science
Languages : en
Pages : 122

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This book explicates the optical controls of antiferromagnetic spins by intense terahertz (THz) electromagnetic waves. The book comprises two key components: (1) the experimental demonstration of the enhancement of a THz magnetic field using a split-ring resonator (SRR) and (2) the control of the direction of magnetization by using the enhanced THz magnetic field to break the symmetry of optically-induced phase transition. These make up the first step leading to future spintronics devices. In the beginning of the book, the author reviews the basics of the ultrafast laser and nonlinear optical techniques as well as the previously achieved experiments to control spin dynamics by THz magnetic fields. In this context, a new experimental protocol is described, in which electron spins in a ferromagnetic material are redirected at the unprecedented level in cooperation with the enhanced THz magnetic field. Subsequently, the author demonstrates that the THz magnetic field is significantly amplified as a nearfield around the SRR structured metamaterial, which is implemented by measuring spin precession in a solid. At the end, the author presents the key experiment in which the amplified THz magnetic nearfield is applied to the weak ferromagnet ErFeO3 along with the femtosecond near-infrared pulse, demonstrating the successful control of symmetry breaking of the spin system due to coherent control of the optically-induced spin reorientation phase transition pathways. The comprehensive introductory review in this book allows readers to overview state-of-the-art terahertz spectroscopic techniques. In addition, the skillful description of the experiments is highly informative for readers in ultrafast magnonics, ultrafast optics, terahertz technology and plasmonic science.

Author: Haitao Chen
Publisher: Open Dissertation Press
ISBN: 9781361000502
Category : Technology & Engineering
Languages : en
Pages : 150

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This dissertation, "On Strain-mediated Magnetoelectric Effects in Multiferroic Composite Nanostructures" by Haitao, Chen, 陈海涛, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Multiferroics which combine two or more order parameters of ferroelectricity, ferromagnetism and ferroelasticity, have drawn great interests in the past few years due to their promising potential of application in sensors, transducers, spintronics and multistate memories. Coupling between the ferroelectricity and ferromagnetism renders the induction of an electric polarization P upon applying a magnetic field, or the induction of a magnetization M upon applying an electric field which is called magnetoelectric coupling effect. There are single phase multiferroics which simultaneously possess ferroelectricity and magnetism in nature. However, these natural multiferroics only exhibit weak magnetoelectric coupling effect at very low temperature which hinders the practical applications. An alternative and more promising choice is to fabricate multiferroic composites. In the multiferroic composite systems, large magnetoelectric coupling effects can be produced indirectly from the strain-mediated interaction even at room temperature and great design flexibility can be obtained. In the present study, two types of multiferroic composite nanostructures are investigated: the vertical heteroepitaxial multiferroic thin films and film-on-substrate heterogeneous bilayers with incorporation of various influences, such as film thickness, misfit strains and flexoelectricity. Since the first fabrication of vertical epitaxial multiferroic nanostructures, great scientific interests have been attracted for the potential large magnetoelectric effects arising from the relaxed substrate constraint and large interfacial area between the ferroelectric and ferromagnetic phases. A three dimensional phase field model is devised to precisely describe the complex strain state of this nanostructure. The simulation results demonstrate that both film thickness and misfit strains are important in determining the magnitude of magnetoelectric effect. Due to the strong strain-mediated magnetoelectric coupling effect in film-on-substrate system with a ferromagnetic thin film directly growing on a thick ferroelectric substrate, precision electric control of local ferromagnetism, i.e. ferromagnetic domain pattern and domain wall properties, are achievable. The results show that the domain pattern of the ferroelectric substrate can be fully transferred onto the as-deposited ferromagnetic thin film. High stability of the magnetic domain is observed when the system is subjected to an external magnetic field. Under an applied electric field, the transferred domain pattern in magnetic film can be either maintained or erased depending on the direction of applied electric field. Moreover, when a pulse of in-plane electric field is applied, the magnetic domain wall motion can be observed in concurrence with the ferroelectric domain wall motion. With the decrease of material size, some effects that can be neglected in bulk materials may play an important role on the overall properties of material, such as flexoelectric effects which describe the induction of polarization from strain gradient. A two dimensional phase field model is adopted to study the influence of flexoelectric effects on the epitaxial ferroelectric films. A thermodynamic phenomenological model is then utilized to analyze the influence of flexoelectric effects on magnetic field induced electric polarization in the multiferroic nanocomposite b