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Shape Anisotropy (shape + anisotropy)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Comparative study of self-assembled CdSe/ZnSe quantum dots grown by variants of conventional MBE

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006
S. Mahapatra
Abstract The morphology, composition, and optical properties of CdSe/ZnSe quantum dots (QDs), grown by conventional molecular beam epitaxy (MBE) and two other variants of the same (low temperature MBE and in-situ annealing), have been compared based on the results of high resolution X-ray diffraction (HRXRD), low temperature micro- and ensemble-photoluminescence (PL), atomic force microscopy (AFM), and Raman spectroscopy (RS) studies. While conventional MBE results in the formation of no discernible QD-like features, by the alternative methods reported here, discrete CdSe QDs, 1.5 to 15 nm high and with a lower density, could be realised. Shape anisotropy of the dots has also been investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

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]

Analysis of magnetic properties in patterned micro-NiFe elements with micro-MOKE and micromagnetics

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004
K. C. Kim
Abstract Magnetic properties of a patterned micro-NiFe element were analyzed with micro-MOKE and micromagnetics. Patterned 8 ,m × 16 ,m NiFe elements have higher coercive field, Hc = 1.9 Oe, for the hard axis than that, Hc = 0.2 Oe, of a 5 mm diameter disk NiFe sample. The magnetization reversal processes have been investigated with the micromagnetic simulation for the various applied field directions. The increase of coercive field in patterned micro-NiFe elements can be attributed to the large shape anisotropy and pinned spins along the edges. Total anisotropy of a 8 ,m × 16 ,m NiFe sample was about 50 Oe. The magnetization reversal field of pinned spins along the edges in patterned micro-NiFe sample was about 500 Oe. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Self-organization and finite size effects in epitaxial ferromagnetic MnAs films on GaAs

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2007
L. Däweritz
Abstract The self-organized striped structure of coexisting ,-MnAs and ,-MnAs, characteristic for MnAs films grown on GaAs(001) by molecular beam epitaxy under As-rich conditions at low temperature, has been studied in samples prepared under conditions closer to the equilibrium. Whereas the period of the stripe pattern is independent on the preparation procedure, the width of the ferromagnetic ,-MnAs stripes increases. Thus, the aspect ratio p between the stripe width L and the stripe thickness t can be varied over a wide range. The magnetic properties of the finite-size magnetic system are investigated as a function of the ratio p at room temperature. The transition from type-I domains with meander-like contrast in the magnetic force microscopy (MFM) image to type-II domains with a line-shaped contrast due to the division of the stripe into N subdomains across the stripe occurs at p ratios expected from a model based on the shape anisotropy. Besides the well-known N = 3 type-II domains also type-II domains with N = 4, 5 were detected. When the stripe width approaches the period of the self-organized structure, the boundary between two neighboring stripes is imaged as chessboard-like contrast in the MFM pattern. The shape of the magnetic hysteresis loops changes with the p ratio or, in other words, with the predominance of in-plane or out-of plane magnetic moments in the demagnetized state. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Light scattering study on hybrid structures of Zn1,x,yCdxMnySe quantum wells with ferromagnetic Co wires

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004
M. Sakuma
Abstract Sub-micron scale hybrid structures of Zn1,x,yCdxMnySe diluted magnetic semiconductor (DMS) quantum wells (QWs) with ferromagnetic Co wires have been fabricated for the purpose of applying local magnetic fields to the DMS-QW. The wire of DMS-QW with the width down to 100 nm was sandwiched between the Co wires. The magneto-optical properties are studied by spin-flip light scattering of paramagnetic Mn-ions in the DMS. The application of uniform magnetic fields higher than 0.25 T has been attained from the Co wires to the DMS-QWs. In addition, the field application from the Co to the DMS-QWs is switched on by weak magnetic fields of 0.03 T due to the magnetic shape anisotropy of the Co wires, which can realize the switching behavior of the spin alignment of Mn-ions in the DMS-QW. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]