Investigation of Magnetic Relaxation Mechanisms and Dynamic Magnetic Properties in Thin Films Using Ferromagnetic Resonance (fmr) Technique PDF Download

Author: Behrouz Khodadadi
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 105

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Book Description
Investigating the damping processes and the behavior of dynamic magnetic properties in ferromagnetic thin films has been an important key towards design and fabrication of different microwave and magnetic recording devices. This thesis discusses the dynamic magnetic properties and also the physics behind different relaxation mechanisms in ferromagnetic thin films using comprehensive experimental investigations by means of broadband ferromagnetic resonance (FMR) technique. In chapter one the basics of ferromagnetic resonance technique and the experimental features of the FMR setup used in this study are discussed, also the FMR data analysis is explained. Chapter two is devoted to the study of the interfacial perpendicular magnetic anisotropy (PMA) and damping parameter in Co2FeAl thin films. In chapter three broadband temperature dependent FMR measurements were carried out on Ni80Fe20/Gd thin films to investigate the behavior of ferromagnetic relaxation, and gyromagnetic ratio as the system goes through the Curie temperature of Gd. In chapter four, the ferromagnetic relaxation mechanisms in ferrites are discussed. The low loss Nikel Ferrite and Lithium ferrite single crystal, thin and ultra-thin films were characterized by detailed FMR measurements to investigate the effect of microstructural defects on the magnetization relaxation. A comprehensive study on the interlayer exchange coupling strength in Co90Fe10/Ru/ Co90Fe10 multilayers is the subject of chapter five, in which the mutual spin pumping is discussed as a recently discovered channel for relaxation in exchange coupled multilayers.

Author: Anjan Barman
Publisher: Springer
ISBN: 3319662961
Category : Technology & Engineering
Languages : en
Pages : 166

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Book Description
This book provides a comprehensive overview of the latest developments in the field of spin dynamics and magnetic damping. It discusses the various ways to tune damping, specifically, dynamic and static control in a ferromagnetic layer/heavy metal layer. In addition, it addresses all optical detection techniques for the investigation of modulation of damping, for example, the time-resolved magneto-optical Kerr effect technique.

Author: Neha Pachauri
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 160

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Book Description
Single crystalline nickel ferrite and lithium ferrite thin films have attracted a lot of research attention recently, because of their unique physical properties for practical applications in next generation technologies, such as monolithic microwave integrated circuits (MMIC) and multiferroic heterostructures. The properties of these materials are closely related to the specific growth method and can be tailored by factors like surface morphology, microstructure and chemical composition. Different thin film growth techniques have been investigated in the past few decades for the fabrication of single crystalline thin films of both these spinel ferrites. However, the difficulty to attain high quality, homogeneous epitaxial films with limited surface and bulk defects and low microwave loss still remains a challenging task. Moreover, there have been very limited reports on the detailed ferromagnetic resonance (FMR) studies of these single crystalline nickel and lithium ferrite thin films, which is an essential aspect to understand the relaxation in magnetization precession (microwave damping) in these materials. In this dissertation work, fabrication and study of structural, magnetic and FMR properties of single crystalline lithium ferrite (LiFe5O8) and nickel ferrite (NiFe2O4) films by direct liquid injection chemical vapor deposition (DLI-CVD) are studied in detail. The growth conditions, which play a crucial role in attaining the desired film morphology and stoichiometry, are optimized to achieve epitaxial, single crystalline lithium ferrite films having low ferromagnetic resonance linewidth coupled with excellent magnetic properties. A detailed ferromagnetic resonance (FMR) study has been done to identify as well as quantify the magnetic relaxation mechanisms in the `as-grown' nickel ferrite films. The broadband frequency, angle and temperature dependent measurements reveal the existence of two-magnon scattering as the active relaxation mechanism for the films.

Author: Max Ken Marcham
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Precessional dynamics are exploited in the operation of high frequency magnetic devices such as magnetic disk drives, non reciprocal microwave devices and spin transfer oscillators. The trajectory of the precession and its damping are of crucial importance. This thesis presents the characterisation of a variety of magnetic thin film structures performed with a range of phase sensitive techniques. It is possible to obtain new insight by utilising the chemical and site specificity of X-ray Magnetic Circular Dichroism (XMCD) to isolate the precession in different chemical species or at distinct sites in the crystal structure of a chosen material. X-ray Ferromagnetic Resonance (XFMR) combines XMCD and Ferromagnetic Resonance (FMR) phenomena in a technique capable of measuring the FMR response of an alloy or multilayer with both chemical and site specificity. To complement the XFMR technique a low temperature Time-Resolved Magneto Optical Kerr Effect (TR-MOKE) setup has been developed. This allowed for the characterisation of samples at temperatures in the range 4 K to room temperature. A frequency swept Vector Network Analyser FMR (VNA-FMR) setup was developed to allow for a fast method for determining the resonance condition and damping of a range of ferromagnetic thin film samples. In addition a TR-X-ray Photoemission Electron Microscopy (TR-XPEEM) setup has been established which allows images to be obtained with magnetic contrast. The combination of the above techniques has lead to studies on rare earth capped spin valve free layers and the measurement of spin pumping in industrially relevant spin valves.

Author: Denys Makarov
Publisher: Springer Nature
ISBN: 3031090861
Category : Science
Languages : en
Pages : 420

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Book Description
This is the first book providing overview of magnetism in curved geometries, highlighting numerous peculiarities emerging from geometrically curved magnetic objects such as curved wires, shells, as well as complex three-dimensional structures. Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines across electronics, photonics, plasmonics and magnetics. This approach provides the means to modify conventional and even launch novel functionalities by tailoring the local curvature of an object. The book covers the theory of curvilinear micromagnetism as well as experimental studies of geometrically curved magnets including both fabrication and characterization. With its coverage of fundamental aspects, together with exploration of numerous applications across magnonics, bio-engineering, soft robotics and shapeable magnetoelectronics, this edited collection is ideal for all scientists in academia and industry seeking an overview and wishing to keep abreast of advances in the novel field of curvilinear micromagnetism. It provides easy but comprehensive access to the field for newcomers, and can be used for graduate-level courses on this subject.

Author: B. J. Nicholson
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 284

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Book Description
This report comprises a selective survey of the present knowledge of the effects of occluded gases and strains on the magnetic properties of Permalloy films, particularlly those which have significance for computer switching applications. Other possible techniques for accomplishing future computer switching functions and magnetic film properties are reviewed. Bulk properties are described and compared with corresponding thin film properties. The magnetic properties of epitaxial Permalloy, epitaxial nickel, epitaxial iron, polycrystalline nickel, and polycrystalline iron films are discussed. The effects of various occluded gases on magnetic film properties are summarized. Stresses present in evaporated films and their significance in determining the magnetic properties of thin films are considered. A selected bibliography of 548 references is included. (Author).

Author: Dr. Orhan Yalçın
Publisher: BoD – Books on Demand
ISBN: 9535111868
Category : Science
Languages : en
Pages : 252

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Book Description
The book Ferromagnetic Resonance - Theory and Applications highlights recent advances at the interface between the science and technology of nanostructures (bilayer-multilayers, nanowires, spinel type nanoparticles, photonic crystal, etc.). The electromagnetic resonance techniques have become a central field of modern scientific and technical activity. The modern technical applications of ferromagnetic resonance are in spintronics, electronics, space navigation, remote-control equipment, radio engineering, electronic computers, maritime, electrical engineering, instrument-making and geophysical methods of prospecting.

Author: Tianhong Xu
Publisher:
ISBN:
Category : Ferromagnetism
Languages : en
Pages : 0

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Book Description
Devices based on magnetic multilayer structures are widely used in the magnetic storage industry. The interfacial magnetic behaviour in these and related structures determines their spin-dependent electron transport properties. This thesis addresses the effects of the surface quality and magnetic properties of Ni thin films and multilayer structures to understand the relationship between the microscopic physical and magnetic structure and macroscopic transport properties. The effects of surface roughness on the magnetic properties of Ni-based thin films, nanowires and multilayer structures have been investigated using linear and nonlinear optical Kerr effect methods, magnetometry and scanning probe microscopy. The magnetic properties of Ni films possessing different surface roughness have been investigated through magnetic second harmonic generation (MSHG) studies. MSHG studies show significant differences between the films' magnetic properties, indicating that surface roughness plays an important role in determining the surface magnetic properties. MSHG studies of Ni nanowire arrays show large magnetic contrast associated with large effective surface areas and additional contributions to the susceptibility, not present in thin films. Electrodeposition of Ni/Cu multilayer structures yield films which display giant magneto-resistance (GMR) behaviour. The effects of layer thickness, roughness and deposition method on their macroscopic magnetoresistance are described. In situ scanning tunnelling microscopy (STM) was employed to study the growth kinetics of Ni films on single crystal Au(111) surfaces through electrodeposition. It has been shown that 2-D or 3-D growth of Ni thin films can be controlled by changing the deposition potentials. The nonlinear optical response from the electrodeposited films indicates that Ni films deposited at a low overpotential possess greater magnetic contrasts and coercive fields. This study reveals the important connection between the film growth mechanisms and the magnetic properties in the ferromagnetic materials. Ultrafast magnetization dynamics of electrodeposited nickel surfaces have been studied using time-resolved MSHG with laser pulses of various pump beam fluence. A fast drop of the second-harmonic intensity within 700 fs after optical excitation is observed which is followed by a partial recovery, within a few picoseconds, indicating the surface magnetic property dependence on the magnetization after the perturbation of the pump laser.

Author: Dongfang Yang
Publisher: BoD – Books on Demand
ISBN: 1803564555
Category : Technology & Engineering
Languages : en
Pages : 224

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Book Description
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Thin films have been employed in many applications to provide surfaces that possess specific optical, electronic, chemical, mechanical and thermal properties. Through ten chapters consisting of original research studies and literature reviews written by experts from the international scientific community, this book covers the deposition and application of thin films.

Author: Takahiro Moriyama
Publisher: ProQuest
ISBN: 9780549821144
Category : Magnetism
Languages : en
Pages :

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Book Description
A microwave study in spintronic devices has been actively pursued in the past several years due to the fertile physics and potential applications. On one hand, a passive use of microwave can be very helpful to analyze and understand the magnetization dynamics in spintronic devices. Examples include ferromagnetic resonance (FMR) measurements, and various microwave spectrum analyses in ferromagnetic materials. The most important chrematistic parameter for the phenomenological analysis on the magnetization dynamics is, so called, the Gilbert damping constant. In this work, a relatively new measurement technique, a flip-chip FMR measurement, to conduct the ferromagnetic resonance measurements has been developed. The measurement technique is equally comparable to a conventional FMR measurement. The Gilbert damping constants were extracted for single ferromagnetic layer, spin vale structures, and magnetic tunnel junctions (MTJs). On the other hand, an active use of microwave yields a great potential for interesting phenomena which give new functionalities into spintronic devices. For instance, a spin wave excitation by an rf field can be used to reduce the switching field of a ferromagnet, i.e. microwave assisted magnetization reversal, which could be a potential application in advanced recording media. More interestingly, a precessing magnetization driven by an rf field can generate a pure spin current into a neighboring layer, i.e. spin pumping effect, which is one of the candidates for generating a pure spin current. A ferromagnetic tunnel junction (MTJ) is one of the important devices in spintronics, which is also the key device to investigate the local and nonlocal magnetization dynamics in this work. Therefore, it is also important to develop high quality MTJs. My work starts from the development of MTJ with AlOx and MgO tunnel barriers where it was found it is crucial to find the proper condition for forming a few nanometers thick tunnel barrier. After obtaining quality MTJs, we proceeded to the study on magnetization dynamics using the MTJs. First interesting phenomenon found in this work is the microwave assisted magnetization reversal (MAMR). It is found that magnetization reversal can be achieved efficiently by an appropriate power and frequency microwave. Moreover, there is a mutual relationship between microwave power and frequency for achieving a maximum switching field reduction. This effect can be very useful in magnetic data storage device which essentially needs to reduce the "effective" coercivity field. In the study of nonlocal magnetization dynamics, we tried to detect the spin accumulation induced by spin pumping effect in FM/NM/I/FM, FM/I/NM and FM/I/FM structures with a microwave excitation (FM: ferromagnetic material, NM: nonmagnetic material, and I: tunnel barrier). Interestingly, in the FM/I/NM and FM/I/FM structures, we observed ~mu-V dc voltage due to the precessing magnetizations. It is found that the dc voltage we observed is much larger than the current the spin pumping theory predicts. Therefore we speculated a new mechanism to explain the results. Although we discussed only a portion of the magnetization dynamics involving nonlinear and nonequilibrium phenomena, it reveals that there is still a fertile physics which has not yet been investigated or explained.