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Magnetization Reversal (magnetization + reversal)

Distribution by Scientific Domains
Physics and Astronomy85%

Selected Abstracts

Highly crystalline cobalt nanowires with high coercivity prepared by soft chemistry

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
G. Viau
Abstract Cobalt nanorods and wires were prepared by reduction of a cobalt salt in a liquid polyol. These particles crystallize with the hcp structure and the growth axis is parallel to the crystallographic c -axis. The kinetic control of the growth allows to vary the mean diameter of the rods and their aspect ratio. Dumbbell like shape particles consisting of a central rod with two conical tips were also obtained. Magnetization curves of oriented wires present very high coercivity (up to 9 kOe) resulting from both a high shape anisotropy and the high magnetocrystalline anisotropy of the hcp cobalt. Micromagnetic simulations showed that the magnetization reversal is shape dependent. The conical tips of the dumbbell particles strongly contribute to the coercivity decrease and must be precluded for permanent magnet applications. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Influence of buffer layers on the texture and magnetic properties of Co/Pt multilayers with perpendicular anisotropy

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007
J. Kanak
Abstract A study on the buffer layer dependence of film texture, surface roughness, and magnetization reversal mechanism in Co/Pt multilayers is presented. Four different buffers are used: (A) 10 nm Cu, (B) 5 nm Ta/10 nm Cu, (C) 5 nm Ta/10 nm Cu/5 nm Ta, and (D) 5 nm Ta/10 nm Cu/5 nm Ta/10 nm Cu. The growth of [2 nm Pt/0.5 nm Co]5/2 nm Pt on top of these buffer layers results in a large variation of film textures and surface morphologies. Samples with a Cu buffer (A) exhibit a low degree of film texture and are relatively rough. MOKE and MFM measurements on these films reveal that the magnetization reverses by the nucleation of numerous small domains due to a large dispersion of the activation energy barrier. Buffer layer structures where the first layer consists of Ta, on the other hand, result in (111)-textured Co/Pt multilayers with a more regular surface morphology. In these samples, magnetization reversal proceeds by fast domain wall movement. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ag buffer layer effect on magnetization reversal of epitaxial Co films

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004
D. H. Wei
Abstract Nano-sized Ag(111) islands were first prepared by using molecular beam epitaxy technique on diluted-hydrofluoric acid etched Si(111) substrate. Epitaxial Co films were then grown onto the Ag films at 100 °C to decrease interdiffusion. The Ag buffer layer designed to form isolated islands with {111} sidewalls on the Si(111) substrate, and provided Co films (111) texture growth to study the correlation between magnetic properties of Co films and Ag buffer layer effect. It reveals that the Ag rough surface acts as a pinning source and Ag {111} sidewalls also plays an important role on the magnetoresistance transition of Co films. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Effect of annealing and ion implantation on interlayer exchange coupling in Fe/Cr multilayers

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
T. Nowak
Abstract Antiferromagnetic interlayer coupling in layered structures exhibiting giant magnetoresistance (GMR) is frequently destroyed by pinholes in the nonmagnetic layers. Therefore pinholes play a key role in limiting performance of GMR structures or magnetic tunnel junctions. We report temperature measurements of magnetization reversal in annealed and ion beam mixed [Fe-3.0 nm/Cr-1.1 nm] multilayers. Analysis of the experimental data shows that both annealing and ion mixing lead to similar subtle changes in the layered structure related to creating pinholes, changes in their density and average volume. [source]

Influence of quadratic contributions in magnetization-induced second harmonic generation studies of magnetization reversal

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2005
V. K. Valev
Abstract Magnetization-induced optical Second Harmonic Generation (MSHG) from an exchange-biased CoO/Fe multilayer produces an asymmetrical hysteresis loop that indicates different magnetization reversal behaviour between the interface and the bulk ferromagnet. A more careful analysis of the data demonstrates that this asymmetry is in fact due to a quadratic dependence on the magnetization of the MSHG intensity. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

On the role of the soft layer in exchange-spring hard/soft magnetic bilayers

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004
D. Bisero
Abstract Bilayers of SmCo/NiFe and SmCo/Co with well-defined in-plane uniaxial anisotropy were grown by dc magnetron sputtering on glass substrates. The magnetization reversal process was investigated by magneto-optic Kerr effect from both sides of the samples, obtaining the hard and soft response separately. The NiFe layers turn out to be exchange coupled to the SmCo films and, for soft layer thicknesses above 30 nm, display reversible demagnetization loops expected from exchange-spring magnets. The experimental NiFe magnetization curve is in good agreement with the theoretical curve obtained by minimizing the magnetic energy in the soft film for an ideal hard/soft bilayer. The soft layer critical thickness above which the exchange spring behavior sets up and its presumed independence on soft layer characteristics are discussed, by comparing the two systems under investigation. We find that SmCo/Co does not fulfil the predictions of the currently accepted theories and that the magnetization reversal of the bilayer is dominated by the Co layer. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Multipolar Ordering in Electro- and Magnetostatic Coupled Nanosystems

CHEMPHYSCHEM, Issue 9 2008
Elena Y. Vedmedenko Dr. habil.
Abstract Electric and magnetic multipole moments and polarizabilities are important quantities in studies of intermolecular forces, non-linear optical phenomena, electrostatic, magnetostatic or gravitational potentials and electron scattering. The experimental determination of multipole moments is difficult and therefore the theoretical prediction of these quantities is important. Depending on purposes of the investigation several different definitions of multipole moments and multipole,multipole interactions are used in the literature. Because of this variety of methods it is often difficult to use published results and, therefore, even more new definitions appear. The first goal of this review is to give an overview of mathematical definitions of multipole expansion and relations between different formulations. The second aim is to present a general theoretical description of multipolar ordering on periodic two-dimensional lattices. After a historical introduction in the first part of this manuscript the static multipole expansion in cartesian and spherical coordinates as well as existing coordinate transformations are reviewed. On the basis of the presented mathematical description multipole moments of several symmetric charge distributions are summarized. Next, the established numerical approach for the calculation of multipolar ground states, namely Monte Carlo simulations, are reviewed. Special emphasis is put on the review of ground states in multipolar systems consisting of moments of odd or even order. The last section is devoted to the magnetization reversal in dense packed nanomagnetic arrays, where the magnetic multipole,multipole interactions play an important role. Comparison between the theory and recent experimental results is given. [source]