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Author : M. M. H. Willekens
Publisher :
ISBN 13 : 9789052823119
Total Pages : 40 pages
Book Rating : 4.8/5 (231 download)
Download or read book Exchange Coupling in Perpendicular Magnetic Multilayers written by M. M. H. Willekens and published by . This book was released on 1994 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Christian Schubert
Publisher : Springer
ISBN 13 : 3319071068
Total Pages : 136 pages
Book Rating : 4.3/5 (19 download)
Download or read book Magnetic Order and Coupling Phenomena written by Christian Schubert and published by Springer. This book was released on 2014-06-03 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents recent developments in magnetic coupling phenomena of ferrimagnetic rare-earth transition-metal Tb-Fe alloys and coupled systems consisting of ferri-/ferromagnetic heterostructures. Taking advantage of the tunability of the exchange coupling between ferrimagnetic and ferromagnetic layers by means of stoichiometry of the Tb-Fe layer, the variable number of repetitions in the Co/Pt multilayer as well as the thickness of an interlayer spacer, it is demonstrated that large perpendicular unidirectional anisotropy can be induced at room temperature. This robust perpendicular exchange bias at room temperature opens up a path towards applications in spintronics.
Author : Lawrence Herman Bennett
Publisher : World Scientific
ISBN 13 : 9789810217679
Total Pages : 400 pages
Book Rating : 4.2/5 (176 download)
Download or read book Magnetic Multilayers written by Lawrence Herman Bennett and published by World Scientific. This book was released on 1994 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on an increasingly important area of materials science and technology, namely, the fabrication and properties of artificial materials where slabs of magnetized materials are sandwiched between slabs of nonmagnetized materials. It includes reviews by experts on the theory and descriptions of the various experimental techniques such as those using nuclear or electron spin probes, as well as optical, X-ray or neutron probes. It also reviews potential applications such as the giant magnetoresistance, and one specialized preparation technique, the electrodeposition. The various chapters are tutorial in nature, making the subject accessible to nonspecialists, as well as useful to researchers in the field.
Author : Kevin Pettit
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (774 download)
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.
Author : John Maurice Mander
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (536 download)
Download or read book Effect of Hybridization on the Exchange Coupling in Magnetic Multilayers written by John Maurice Mander and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Christopher Hugh Marrows
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (817 download)
Download or read book Indirect Exchange Coupling in Sputtered Magnetic Multilayers written by Christopher Hugh Marrows and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the design, construction, and use of a sputter deposition facility at the University of Leeds for the growth of magnetic multilayer samples. Now completed, the machine is a UHV sputtering facility, capable of growing up to 15 samples of arbitrary complexity under computer control in a single vacuum cycle. The system currently has five sputter targets. The system was used to grow Co/Cu multilayers. It was found that the level of residual gas in the chamber is of primary importance in determining the final quality of the samples. A good vacuum is required to achieve good antiferromagnetic coupling between adjacent Co layers in the multilayer stack. Consequentially the giant magnetoresistance of such samples is very high. A poor vacuum leads to poor coupling between Co layers, and the magnetoresistance of such samples is minimal. When grown under clean conditions the giant magnetoresistance of the Co/Cu multilayers was very high - as much as 75% at room temperature, rising to 130% at 4.2K. Coupling oscillations as the Cu spacer thickness was varied were strong, whilst none were detected as a function of Co thickness. It was found that the >
Author : Xiaosong Ji
Publisher :
ISBN 13 :
Total Pages : 270 pages
Book Rating : 4.:/5 (228 download)
Download or read book Perpendicular Anisotropy and Exchange Bias in Magnetic Multilayers written by Xiaosong Ji and published by . This book was released on 2007 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Valentin Fadeev
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (12 download)
Download or read book Spin Transport and Exchange Coupling in Ballistic Magnetic Multilayers written by Valentin Fadeev and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : U. Hartmann
Publisher : Springer Science & Business Media
ISBN 13 : 3662041219
Total Pages : 331 pages
Book Rating : 4.6/5 (62 download)
Download or read book Magnetic Multilayers and Giant Magnetoresistance written by U. Hartmann and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unified overview of recent progress in a growing, multi-disciplinary field places special emphasis on the industrial applications of magnetic multilayered materials. The text describes a wide range of physical aspects, together with experimental and theoretical methods.
Author : 王柏堯
Publisher :
ISBN 13 :
Total Pages : 144 pages
Book Rating : 4.:/5 (635 download)
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:
Author : Hang Chen
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.5/5 (355 download)
Download or read book Magnetic Dynamics in Magnetic Multilayers and Spintronic Devices written by Hang Chen and published by . This book was released on 2021 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: A critical issue in spintronic devices is how to efficiently switch the magnetization of a nanomagnet. The switching is typically occurred at ferromagnetic resonant frequency. One of the very desired features is to enhance the resonant frequency so as to increase the switching speed. In this thesis. we use optical mode in coupled FM bilayers to significantly enhance the resonance frequency because the ferromagnetic exchange coupling is much stronger compared with other effective field introduced by, for example, strain or anisotropy. we theoretically and experimentally study the resonant frequency in Co90Fe10/Ta/(Ni80Fe20)18́2xCux trilayer. we also validate the theoretical model with experimental results and use the theoretical model to further design heterostructures with desired properties such as enhanced intensity in OM. All of our experimental results are fully explained by our model which also allows us to identify the coupling mechanism as Neel "orange-peel" coupling and extract the interlayer coupling strength. In current magnetic random access memories (MRAMs), the magnetization is switched via spin transfer torques (STT) or spin orbit torques (SOTs). In this thesis, we use a time-resolved (TR) Magneto-optic Kerr effect (TRMOKE) to investigate the SOT-induced magnetization dynamics in Py/Pt and Ta/CoFeB heterostructures. We have answered three questions as we set to explore: (1) the field-like torque determines initial oscillation magnitude and the damping-like torque determines the final steady position; (2) both the effect field of damping-like toque hDL and field-like torque hFL can be extracted from the TRMOKE spectrum, and (3) the ratio hDL/ hFL measured from dynamics are the same as those measured at low frequency. Finally, we also explore the way of using voltage to switch the magnetization in order to significantly reduce the energy consumption. We employed an antiferromagnetic Cr2O3 film with net a net magnetization at the film surface. The surface magnetization can be isothermally switched via applied electric field (voltage), enabling "writing" function in the memory cell. We solved various challenges in developing the final device including (1) exchange coupling between the surface magnetization and the magnetization in a ferromagnetic heterostructure of Co/Pd multilayer, (2) the exchange coupling between Co/Pd and CoFeB which has perpendicular magnetization and serves as a bottom electrode of magnetic tunnel junction for readout. (3) the leakage issue of Cr2O3, (4) the contact to middle layer that is less than 5 nm thick, and (5) device layout and detailed fabrication steps. Although we did not have time to fully demonstrate the devices, all key steps have been well resolved.
Author : Amritpal Singh
Publisher :
ISBN 13 :
Total Pages : 91 pages
Book Rating : 4.:/5 (895 download)
Download or read book Multi-layer Magnetism and Thermal Stability in Perpendicular Magnetic Tunnel Junctions written by Amritpal Singh and published by . This book was released on 2014 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal stability is one of the critical issues for applications of nano-magnets for spin-logic applications. Our work is focused on the thermal stability in perpendicular magnetic tunnel junctions (p-MTJs) for MRAM and STT-RAM purposes. Most of the research so far has been focused on p-MTJs based on CoFeB/MgO interfacial anisotropy as the sandwich structures with bcc ferromagnetic electrodes and MgO spacer have large magnetoresistance. It has been demonstrated that this interfacial anisotropy by itself is not sufficient to reduce the p-MTJ diameter down to 20 nm. To overcome this problem, we have proposed and investigated hard-soft composite structures: [Co/Pt multilayers]/ (non-magnetic element) /CoFeB/MgO, to control the perpendicular magnetic anisotropy (PMA) of the CoFeB soft layer by exchange coupling with Co/Pt multilayers having bulk anisotropy. Ta has been studied as the first non-magnetic insertion element, since it helps in crystallization of CoFeB by absorbing the B. The other elements studied as insertions are V and Zr, since they have low damping constants. A micromagnetic model has been set up on the basis of experimental results and ab-initio calculations to study the effect of insertion thickness and damping parameter on switching current density and switching time. To understand the mechanism of CoFeB/MgO interfacial anisotropy, low temperature scaling of interface anisotropy (Ks(T)) and saturation magnetization (Ms(T)) is measured, since at low temperature (T), Ks(T) vs Ms(T) scaling is sensitive to the details of the anisotropy mechanism. For the first time, we experimentally show that for CoFeB/MgO, Ks(T) scales as Ms(T) 2.2, hence indicating the two-ion type anisotropy as the dominant mechanism.
Download or read book Exchange Coupling and Noncollinear Magnetic States in Ni/Fen/Ni(1 0 0) Multilayers written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Michael Hunziker
Publisher :
ISBN 13 :
Total Pages : 52 pages
Book Rating : 4.:/5 (838 download)
Download or read book Molecular-orbital Model of Heat-induced Effective Exchange Coupling in Magnetic Multilayers written by Michael Hunziker and published by . This book was released on 2000 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Alex Martin Robinson
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (594 download)
Download or read book The Tight-binding Torque-method for the Exchange Coupling in Magnetic Multilayers written by Alex Martin Robinson and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Robert James Hughes
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (855 download)
Download or read book Magneto-oscillatory Exchange Coupling in Magnetic Multilayers with Cr0!0!0!V0! and Cr0!0!0!Mo0! Spacers written by Robert James Hughes and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Monika Arora
Publisher :
ISBN 13 :
Total Pages : 131 pages
Book Rating : 4.:/5 (112 download)
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.
