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Interrelation Between Perpendicular Magnetic Anisotropy And Exchange Coupling In Low Dimensional Ferromagnetic Antiferromagnetic Ultrathin Film Systems
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Book Synopsis Interrelation Between Perpendicular Magnetic Anisotropy and Exchange Coupling in Low Dimensional Ferromagnetic-antiferromagnetic Ultrathin Film Systems by : 王柏堯
Download or read book Interrelation Between Perpendicular Magnetic Anisotropy and Exchange Coupling in Low Dimensional Ferromagnetic-antiferromagnetic Ultrathin Film Systems written by 王柏堯 and published by . This book was released on 2009 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Magnetic Properties of Antiferromagnetic Oxide Materials by : Lamberto Duò
Download or read book Magnetic Properties of Antiferromagnetic Oxide Materials written by Lamberto Duò and published by John Wiley & Sons. This book was released on 2010-04-16 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first focused treatment on a hot topic highlights fundamental aspects as well as technological applications arising from a fascinating area of condensed matter physics. The editors have excellent track records and, in light of the broadness of the topic, retain the focus on antiferromagnetic oxides. They thus cover such topics as dichroism in x-ray absorption, non-magnetic substrates, exchange bias, ferromagnetic-antiferromagnetic interface coupling and oxide multilayers, as well as imaging using soft x-ray microscopy. The result is a very timely monograph for solid state physicists and chemists, materials scientists, electrical engineers, physicists in industry, physical laboratory technicians, and suppliers of sensors.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2540 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Confined Magnon Modes and Anisotropic Exchange Interaction in Ultrathin Co Films by : Ying-Jiun Chen
Download or read book Confined Magnon Modes and Anisotropic Exchange Interaction in Ultrathin Co Films written by Ying-Jiun Chen and published by Logos Verlag Berlin GmbH. This book was released on 2017 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fundamental need in wireless communication and modern computer processors is to fabricate faster, smaller, and lower power-consumption circuits. A promising approach is the utilization of spin waves, or rather, magnons in ferromagnetic films. Quantum confinement in ultra-thin films permits the coexistence of several exchange-dominated magnon modes with terahertz-range frequencies and sub-nanometer length scales. By means of spin-polarized electron energy loss spectroscopy (SPEELS), these exchange-dominated terahertz magnons are directly probed in ultra-thin cobalt films on Ir(001), Cu(001) and Pt(111) single crystal surfaces. The dispersion relation of the quantized magnon modes depends particularly on the interatomic exchange interaction in individual layers. By tuning the exchange interaction, modes with opposite group velocities, and thus an opposite propagation direction of the wave packets, can be generated. Ab initio theoretical calculations as well as an analytical Heisenberg model reveal a spatial localization of the modes at the surface, interior, and interface of the film that opens an experimental access to the layer-dependent magnetic properties. In itinerant ferromagnets like cobalt the magnetic properties depend sensitively on many-body correlation effects in the electronic structure. Here, it is shown for the first time that spin-dependent correlations lead to a pronounced renormalization of the energy of the highest magnon mode by up to 260 meV, explaining the significant overestimation of theoretically predicted magnon energies and interatomic exchange interaction found in literature.
Book Synopsis Magnetic Properties of Coupled Magnetic Thin Films by : Changyeon Won
Download or read book Magnetic Properties of Coupled Magnetic Thin Films written by Changyeon Won and published by . This book was released on 2005 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Stabilization, Dynamics, and Control of Chiral Magnetic Textures in Thin-film Multilayers by : Jeffrey Adams Brock
Download or read book Stabilization, Dynamics, and Control of Chiral Magnetic Textures in Thin-film Multilayers written by Jeffrey Adams Brock and published by . This book was released on 2022 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we investigate the stabilization and dynamics of chiral domain walls and skyrmions in several ferromagnet/heavy metal thin-film multilayers. In each material system, the ferromagnet/heavy metal interfaces were engineered to give rise to an interfacial Dzyaloshinskii-Moriya interaction (iDMI)--a spin-orbit coupling mediated effect known to promote the formation of chiral magnetic textures. Throughout several comprehensive studies (presented herein as separate chapters), we explore the stabilization and dynamics of skyrmions in three distinct types of material systems: Thin-films close to experiencing a spin-reorientation transition, ultrathin films with low ferromagnetic exchange and high perpendicular magnetic anisotropy, and thick multilayers with large perpendicular magnetic anisotropy. Through experimental and theoretical studies, we explore the processes by which skyrmions can be created and moved in response to both quasi-static and transient electrical currents, magnetic fields, and temperature changes. In all cases, the systematic variation of material properties and experimental conditions to better understand and control the mechanisms by which skyrmions are stabilized is a key underlying theme. In another thrust, we have studied the field-driven dynamics of chiral domain walls and have characterized a new effect in which magnetic stripe domains with chiral domain walls unidirectionally expand in response to applied magnetic fields, with growth symmetries that cannot be understood from the static energy frameworks typically employed to understand the impact of the interfacial Dzyaloshinskii-Moriya interaction in thin-film systems. Using analytical models, we have found that the in-plane torques generated by perpendicular magnetic fields stabilize steady-state domain wall magnetization profiles that are highly asymmetric in elastic energy, resulting in abnormal growth behaviors that are in line with the experimental findings. Building on this understanding of the field-driven dynamics of stripe domains, we expand this understanding to the growth directionalities observed when stripe domain motion is induced by spin-orbit torque.
Book Synopsis Origin of Perpendicular Magnetic Anisotropy in Co/Ni Multilayers and Their Use in STT-RAM by : Monika Arora
Download or read book Origin of Perpendicular Magnetic Anisotropy in Co/Ni Multilayers and Their Use in STT-RAM written by Monika Arora and published by . This book was released on 2017 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic properties of (111)-textured SAF/Cu/FL multilayer film structures were optimized by varying individual layer thickness and sputtering conditions. The SAF is a synthetic antiferromagnet consisting of Co/Ni multilayers coupled antiferromagnetically across a Ru spacer layer, and the FL is a free layer consisting of a single Co/Ni multilayer. The Co and Ni thicknesses were varied to obtain larger perpendicular magnetic anisotropy. The perpendicular magnetic anisotropy, saturation magnetization, damping and zero-frequency line broadening of the Co/Ni multilayers strongly depend on the number of bilayers. With increasing Cu seed-layer thickness, the texture of the Co/Ni multilayers improves while the grain size and film roughness increase. The increase in grain size results in the reduction of the direct exchange coupling between magnetic grains, which enhances the coercivity of the SAF and the FL. Experimentally measured coercivities of the SAF and FL are compared with calculations obtained from a coherent rotation model. The effect of the role of the Co/Cu interface in the magnetoresistance, is also discussed. Spin-transfer-torque induced switching is investigated in 200 nm diameter circularly shaped, perpendicular magnetized nanopillars. The SAF layer is used as a reference layer to minimize the dipolar field on the free layer. The use of Pt and Pd was avoided to lower the spin-orbit scattering in magnetic layers and intrinsic damping in the free layer, and therefore, reduce the critical current required for spin-transfer-torque switching. In zero magnetic field the critical current required to switch the free layer from the parallel to antiparallel (antiparallel to parallel) alignment is 5.2 mA (4.9 mA). Given the volume of the free layer, VFL = 1.01×10-22 m3, the switching efficiency, Ic/(VFL m0Hc), is 5.28×1020 A/Tm3, twice as efficient as any previously reported device with a similar structure. Variation in perpendicular magnetic anisotropy of (111) textured Au/N×[Co/Ni]/Au films as a function of number of bilayer repeats N is studied. The experimental measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N ≤ 10 and then moderately decreases for N> 10. The model we propose reveals that the decrease of the anisotropy for N 10 is predominantly due to the reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N 10 is due to the reduction in the magnetocrystalline and the surface anisotropies.
Book Synopsis Exchange Anisotropy in Ferromagnetic/antiferromagnetic Bilayers by : Ilya Krivorotov
Download or read book Exchange Anisotropy in Ferromagnetic/antiferromagnetic Bilayers written by Ilya Krivorotov and published by . This book was released on 2002 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1076 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Magnetic Exchange Phenomena in Reduced Dimensions Studied by Neutron Scattering by : Thomas Saerbeck
Download or read book Magnetic Exchange Phenomena in Reduced Dimensions Studied by Neutron Scattering written by Thomas Saerbeck and published by . This book was released on 2012 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Truncated abstract] This thesis deals with magnetic exchange interactions in thin lm magnetic materials focusing on phenomena related to intrinsic parameters of magnetic, structural and chemical order. In particular, the investigation is of two magnetic thin film systems, a Cu0.94Mn0.06/Co multilayer displaying a temperature-dependent magnetic ordering due to exchange coupling originating from dilute paramagnetic Mn spins, and thin films of chemical order modulated FePt3, showing a unique self-exchange bias effect. Detailed real-space models of the magnetic structure are obtained using polarized neutron reffectometry and high-angle neutron diffraction, speciffcally chosen to probe interface and bulk magnetic characteristics, respectively, in connection with complementary structural and magnetic characterization tools. It will be discussed, how the random distribution of dilute magnetic impurity centers in the Cu0.94Mn0.06/Co multilayers leads to a temperature-dependent interlayer exchange coupling with a strong biquadratic component. This manifests in an in-plane magnetic domain structure with a canted magnetization, i.e. a deviation from collinear alignments of external magnetic field and magnetization. The domain magnetizations show a high degree of vertical correlation in the form of columns throughout the multilayer, in which the sense of canting alternates in sign for each subsequent magnetic layer. Detailed analysis of temperature and field dependences of the magnetic structure lead to fundamental exchange energies, which are utilized in constructing a phenomenological model of exchange interactions between dilute magnetic impurities and the ferromagnetic layers. In addition to this, the second study deals with the effect of chemical order of the constituent atoms in the alloy FePt3 on the magnetic order on atomic and sub-micrometer scales. Depending on the long-range chemical order, ferromagnetic or antiferromagnetic grains exist below the respective transition temperatures. As such, the system constitutes a new way of controlling the magnetic composition of thin lms without changing the materials composition, stoichiometry or lattice structure. The interfacing of the two magnetic grains leads to the observation of a unique self-exchange bias effect. Based on studies in thin films of FePt3 with varying degree of chemical order and the evolution of exchange bias with respect to interface and volume of the chemically ordered grains, a mono-stoichiometric FePt3 ferromagnetic/antiferromagnetic multilayer is presented. Analysis of the magnetic structure in the arti cially layered thin film elucidates the magnetic composition and origin of the observed exchange bias. Due to the unique mono-stoichiometric structure, the system opens possibilities to study magnetic phenomena in perfect lattice-matched systems...
Book Synopsis Growth Induced Magnetic Anisotropy in Amorphous Thin Films. Annual Progress Report Year 1, November 4, 1994--October 31, 1995 by :
Download or read book Growth Induced Magnetic Anisotropy in Amorphous Thin Films. Annual Progress Report Year 1, November 4, 1994--October 31, 1995 written by and published by . This book was released on 1995 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work in the past year has primarily involved three areas of magnetic thin films: amorphous rare earth-transition metal alloys, epitaxial COPt3 thin films, and exchange coupled antiferromagnetic insulators. In the amorphous alloys, the authors have focused on understanding the cause and the effect of the growth-surface-induced perpendicular magnetic anisotropy. Using the results of previous work, they are able to control this anisotropy quite precisely. This anisotropy is predicted to have dramatic and as-yet unobserved effects on the underlying nature of the magnetism. The work on the epitaxial Co-Pt alloys was originally undertaken as a comparison study to the amorphous alloys. The authors have discovered that these alloys exhibit a remarkable new phenomena; a surface-induced miscibility gap in a material which is believed to be completely miscible in the bulk. This miscibility gap is 100% correlated with the perpendicular anisotropy, although the connection is not yet clear, and is presumably linked to a magnetic energy of mixing which tends to drive a material towards clustering. The problem of exchange coupling in multilayers impacts many of the current research areas in magnetism. NiO/CoO multilayers can be prepared with coherent interfaces. The specific heat shows unambiguously the ordering of the spins in the layers. The results show clearly the transition from a single transition temperature to two distinct transitions with increasing thickness of the individual layers. From this data, the authors are able to determine the interface magnetic exchange coupling constant and the effect on the transition temperature of finite layer thickness.
Book Synopsis Ab Initio Investigations of Magnetic Properties of Ultrathin Transition Metal Films on 4d Substrates by : Ali Al-Zubi
Download or read book Ab Initio Investigations of Magnetic Properties of Ultrathin Transition Metal Films on 4d Substrates written by Ali Al-Zubi and published by Forschungszentrum Jülich. This book was released on 2010 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Ferromagnetic Relaxation and Interlayer Exchange Coupling in Magnetic Films and Heterostructures by : Alexander Yulievich Dobin
Download or read book Ferromagnetic Relaxation and Interlayer Exchange Coupling in Magnetic Films and Heterostructures written by Alexander Yulievich Dobin and published by . This book was released on 2003 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Science Abstracts written by and published by . This book was released on 1992 with total page 1228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Magnetic Order and Coupling Phenomena by : Christian Schubert
Download or read book Magnetic Order and Coupling Phenomena written by Christian Schubert and published by . This book was released on 2014-06-30 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Exchange Coupling and Giant Magnetoresistance in Nickel-iron/copper Multilayers by : Kevin Pettit
Download or read book Exchange Coupling and Giant Magnetoresistance in Nickel-iron/copper Multilayers written by Kevin Pettit and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years interlayer exchange coupling and giant magnetoresistance (GMR) in transition metal ferromagnet/nonmagnetic multilayers have been extensively studied. Bilinear interlayer exchange favors the collinear alignment of the magnetization of adjacent ferromagnetic layers, oscillates with the thickness of the non-magnetic spacer layer, and has been observed in a large number of magnetic multilayer and trilayer systems. Biquadratic exchange favors the perpendicular alignment of the magnetization of adjacent ferromagnetic layers and has been observed in several magnetic multilayer and trilayer systems. Unlike bilinear exchange, the origins of biquadratic exchange are uncertain. Generally, biquadratic exchange is significantly weaker than bilinear exchange. The connection between the magnetic configuration, which is determined by the interlayer coupling, and the magnetoresistance is well established. The GMR effect occurs when the antiferromagnetically aligned moments of alternating magnetic layers are brought into alignment by an external magnetic field. This causes a dramatic drop in the electrical resistance. Much of the interest in magnetic multilayers stems from the many possible applications of the GMR effect. This work is a study of biquadratic coupling and its effects on the magnetic phase diagram and giant magnetoresistance of sputter grown single crystal NiFe/Cu multilayers. It is often difficult to determine the bilinear and biquadratic coupling strengths separately, particularly in samples with pinhole defects in the spacer layers, because the zero field configuration of the moments is not easily determined. However, I will show that under certain conditions biquadratic coupling can lead to configurations in which the net magnetization of the coupled magnetic moments is not aligned parallel to the applied magnetic field. In samples with magnetocrystalline anisotropy, these asymmetric configurations lead to a novel minimum in the GMR at low fields when the field is applied along the hard axis of magnetization. In such cases, the bilinear and biquadratic coupling strengths can be determined from resistance measurements only. In this work the magnetic phase diagram is calculated for a two layer system with bilinear coupling, biquadratic coupling and magnetocrystalline anisotropy. New asymmetric configurations, some of which cannot be determined analytically, are found. Numerical simulations confirm the contribution of these configurations to the GMR and the accuracy of the interlayer coupling strengths extracted from the magnetoresistance data. These measurements indicate that the biquadratic coupling can be considerably stronger than predicted theoretically. The data are found to be inconsistent with the intrinsic, loose spin, dipole field, and fluctuation models of biquadratic coupling. To explain the data I propose a new model in which ferromagnetic coupling through pinholes in the spacer layer, combined with the antiferromagnetic bilinear coupling, frustrates the magnetic layers and leads to orthogonal coupling. Unlike the fluctuation model, the pinhole-frustration model allows for very strong biquadratic coupling. Although the pinhole mechanism can lead to biquadratic coupling, closer analysis reveals that the bilinear-biquadratic formalism may break down for strong frustration.
