Magnetoelectric Response in Low-Dimensional Frustrated Spin Systems

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Publisher : Springer Science & Business Media
ISBN 13 : 4431540911
Total Pages : 135 pages
Book Rating : 4.4/5 (315 download)

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Book Synopsis Magnetoelectric Response in Low-Dimensional Frustrated Spin Systems by : Shinichiro Seki

Download or read book Magnetoelectric Response in Low-Dimensional Frustrated Spin Systems written by Shinichiro Seki and published by Springer Science & Business Media. This book was released on 2012-08-27 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Magnetism and Transport Phenomena in Spin-Charge Coupled Systems on Frustrated Lattices

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Publisher : Springer
ISBN 13 : 443155663X
Total Pages : 142 pages
Book Rating : 4.4/5 (315 download)

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Book Synopsis Magnetism and Transport Phenomena in Spin-Charge Coupled Systems on Frustrated Lattices by : Hiroaki Ishizuka

Download or read book Magnetism and Transport Phenomena in Spin-Charge Coupled Systems on Frustrated Lattices written by Hiroaki Ishizuka and published by Springer. This book was released on 2015-07-13 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, magnetism and transport phenomena in spin-charge coupled systems on frustrated lattices are theoretically investigated, focusing on Ising-spin Kondo lattice models and using a combination of Monte Carlo simulation and other techniques such as variational calculations and perturbation theory. The emphasis of the study is on how the cooperation of spin-charge coupling and geometrical frustration affects the thermodynamic properties of the Kondo lattice models; it presents the emergence of various novel magnetic states, such as the partial disorder, loop-liquid, and spin-cluster states. The thesis also reveals that the magnetic and electronic states and transport properties of these models demonstrate peculiar features, such as Dirac half-metals, anomalous Hall insulators, and spin Hall effects. Study of novel magnetic states and exotic transport phenomena in Kondo lattice systems is a field experiencing rapid progress. The interplay of charge and spin degrees of freedom potentially gives rise to various novel phases and transport phenomena which are related to strongly correlated electrons, frustrated magnetism, and topological states of matter. The results presented in this thesis include numerical calculations that are free from approximations. Accordingly, they provide reliable reference values, both for studying magnetism and transports of related models and for experimentally exploring novel states of matter in metallic magnets.

Preparation, characterization and investigations of electrical and magnetic properties of some ferrites

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Publisher : GRIN Verlag
ISBN 13 : 3640977130
Total Pages : 163 pages
Book Rating : 4.6/5 (49 download)

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Book Synopsis Preparation, characterization and investigations of electrical and magnetic properties of some ferrites by : Sagar Shirsath

Download or read book Preparation, characterization and investigations of electrical and magnetic properties of some ferrites written by Sagar Shirsath and published by GRIN Verlag. This book was released on 2011-08-05 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Doctoral Thesis / Dissertation from the year 2010 in the subject Physics - Nuclear Physics, Dr. Babasaheb Ambedkar Marathwada University (-), course: PH.D., language: English, abstract: Wide scope is available to study these aspects of ferrite which at present to our knowledge was not probe by researchers. In relevance to the ever expanding possibilities, and potential that is available with the ferrite materials, the scope of presently undertaken work is designed carefully by selecting suitable ferrite and dopants. A sincere attempt was made to extract fruitful, exhaustive and, systematic information regarding structural, cation distribution, electrical, dielectric and magnetic aspects of the ferrite systems under investigations. In the present study, the properties of nickel ferrites substituted by diamagnetic Zn2+, non-magnetic trivalent In3+ ions and tetravalent Ce4+ ions are studied for various compositions. The properties are investigated with a view to understand the effect of divalent, trivalent and tetravalent substitution in nickel ferrite. The thesis consists of five chapters. Chapter 1 related to Scope, problem statement, theory of magnetism, ferrites, background, motivation and aim of the present work, properties of the samples under investigations, objective and outline of thesis. Chapter 2, 3 and 4 related to results and discussion of structural, electrical and magnetic properties of Ni1-xZnxFe2O4, NiInxFe2-xO4 and Ni1-2xCexFe2O4 ferrite system respectively. Chapter 5 gives the summary, discussion and conclusion on Zn, In and Ce substituted nickel ferrite. On summarizing the results obtained on Ni-Zn, Ni-In and Ni-Ce spinel ferrites it can be concluded that; • The structural properties are found to be varying in all the three systems. The lattice parameter of Ni ferrite systems increases with increasing valancy of dopants (Zn2+, In3+ and Ce4+). • The other prominent parameter of our structural study i.e. porosity reflects that with tetravalent substitution minimum porosity can be achieved. • The particle size does not show any significant difference in their values when substituted with Zn2+, In3+ and Ce4+. • The band frequency in IR spectra slightly changes with the substitution of Zn2+, In3+ and Ce4+. • The magnetic properties are very much affected as can be seen from the values of saturation magnetization of Zn2+, In3+ and Ce4+ substituted nickel ferrite.

Local Investigation of Single Magnetic Molecules with Scanning Tunneling Microscopy

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Publisher : KIT Scientific Publishing
ISBN 13 : 3731508192
Total Pages : 146 pages
Book Rating : 4.7/5 (315 download)

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Book Synopsis Local Investigation of Single Magnetic Molecules with Scanning Tunneling Microscopy by : Chen, Jinjie

Download or read book Local Investigation of Single Magnetic Molecules with Scanning Tunneling Microscopy written by Chen, Jinjie and published by KIT Scientific Publishing. This book was released on 2019-01-18 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: We worked on different magnetic molecules containing 3d and 4f magnetic centers. Their growth on metallic surfaces, topographies, spin states, magnetic properties and electron transport were locally investigated by using scanning tunneling microscopy (STM) at temperatures down to 30mK. The main achievement of this dissertation reveals the abrupt switching of crystal fields during formation of molecular contacts.

Nonlocal and Local Magnetization Dynamics Excited by an RF Magnetic Field in Magnetic Multilayers

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Publisher : ProQuest
ISBN 13 : 9780549821144
Total Pages : pages
Book Rating : 4.8/5 (211 download)

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Book Synopsis Nonlocal and Local Magnetization Dynamics Excited by an RF Magnetic Field in Magnetic Multilayers by : Takahiro Moriyama

Download or read book Nonlocal and Local Magnetization Dynamics Excited by an RF Magnetic Field in Magnetic Multilayers written by Takahiro Moriyama and published by ProQuest. This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.