scholarly journals Magnetic-Coupling Properties in Polycrystals

1998 ◽  
Vol 30 (3-4) ◽  
pp. 167-189 ◽  
Author(s):  
L. Fuentes
Keyword(s):  
Texture Analysis ◽  
Spherical Harmonics ◽  
Magnetic Coupling ◽  
Surface Representation ◽  
Magnetic Subsystem ◽  
Peculiar Behaviour ◽  
Surface Representations ◽  
Piezomagnetic Effects ◽  
Symmetry Operations

Quantitative Texture Analysis procedures for characterisation of polycrystal pyromagnetic, magnetoelectric and piezomagnetic effects are proposed. The considered phenomena link the thermic, electric and elastic subsystems of a given body with its magnetic subsystem. Brief resumes of required thermodynamic, tensor and texture methods are given. Peculiar behaviour of magnetic (axial-tensor) quantities under colour symmetry operations is described. The use of Neumann's Principle in the investigation of the considered effects is discussed. Surface representation of magnetic-coupling properties is analysed in detail. Colour symmetry, combined with the axial nature of the related tensors, determines the shapes of properties' surfaces. Bunge's spherical harmonics treatment of surface representations is adapted to axial-tensor cases. Computer-generated cases of pyromagnetic, magnetoelectrie and piezomagnetic textures are solved.

scholarly journals Surface Representation of Polycrystal Physical Properties: All Crystal Classes, Simple Average Approximation

1996 ◽  
Vol 28 (1-2) ◽  
pp. 81-92 ◽  
Author(s):  
O. Raymond ◽  
L. Fuentes ◽  
J. I. Gómez
Keyword(s):  
Physical Properties ◽  
Spherical Harmonics ◽  
Surface Representation ◽  
Surface Representations ◽  
Average Approximation ◽  
Simple Average

Algorithms for polycrystal physical properties estimation are presented. Bunge's spherical harmonics treatment of surface representations, under simple average approximation, is applied. Specific formulae for so-called longitudinal magnitudes are given. Physical properties associated to tensors of second-, third- and fourth-rank are considered. All crystal and sample symmetries are covered.

scholarly journals Computer-Oriented Real Spherical Harmonics for Texture and Properties Analyses

1996 ◽  
Vol 28 (1-2) ◽  
pp. 93-104 ◽  
Author(s):  
O. Raymond ◽  
L. Fuentes ◽  
J. I. Gómez
Keyword(s):  
Texture Analysis ◽  
Spherical Harmonics ◽  
Three Dimensional ◽  
Sample Point ◽  
Computer Implementation ◽  
Point Groups

An algorithm system to generate symmetric real functional bases for Quantitative Texture Analysis (QTA) is presented. A review of the analytical conditions to be satisfied by the considered functions is given. Suitable two- and three-dimensional bases are proposed. All crystal and sample point groups are analyzed. Computer implementation of the suggested algorithms is straightforward.

Spherical harmonics in texture analysis

2003 ◽  
Vol 370 (1-4) ◽  
pp. 253-268 ◽  
Author(s):  
Helmut Schaeben ◽  
K.Gerald van den Boogaart
Keyword(s):  
Texture Analysis ◽  
Spherical Harmonics

Zonal and tesseral harmonic perturbations of an artificial satellite

1966 ◽  
Vol 25 ◽  
pp. 323-325 ◽  
Author(s):  
B. Garfinkel
Keyword(s):  
Angular Velocity ◽  
Spherical Harmonics ◽  
Artificial Satellite ◽  
Compact Form ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Secular Variations ◽  
Tesseral Harmonics

The paper extends the known solution of the Main Problem to include the effects of the higher spherical harmonics of the geopotential. The von Zeipel method is used to calculate the secular variations of orderJmand the long-periodic variations of ordersJm/J2andnJm,λ/ω. HereJmandJm,λare the coefficients of the zonal and the tesseral harmonics respectively, withJm,0=Jm, andωis the angular velocity of the Earth's rotation. With the aid of the theory of spherical harmonics the results are expressed in a most compact form.

Peculiarity Parameters

1976 ◽  
Vol 32 ◽  
pp. 233-254
Author(s):  
H. M. Maitzen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Theoretical Work ◽  
Observational Evidence ◽  
Rotator Model ◽  
Peculiar Behaviour ◽  
Field Spectrum ◽  
Oblique Rotator ◽  
Ap Stars ◽  
The Way

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).

Grain separation enhanced magnetic coercivity in Pt/Co multilayers.

1993 ◽  
Vol 51 ◽  
pp. 1038-1039 ◽  
Author(s):  
G.A. Bertero ◽  
R. Sinclair
Keyword(s):  
Remanent Magnetization ◽  
Strong Influence ◽  
Uniaxial Anisotropy ◽  
Magnetic Coupling ◽  
Recording Media ◽  
Magnetic Media ◽  
Signal To Noise ◽  
Out Of Plane ◽  
Longitudinal Recording ◽  
The Relationship

Pt/Co multilayers displaying perpendicular (out-of-plane) magnetic anisotropy and 100% perpendicular remanent magnetization are strong candidates as magnetic media for the next generation of magneto-optic recording devices. The magnetic coercivity, Hc, and uniaxial anisotropy energy, Ku, are two important materials parameters, among others, in the quest to achieving higher recording densities with acceptable signal to noise ratios (SNR). The relationship between Ku and Hc in these films is not a simple one since features such as grain boundaries, for example, can have a strong influence on Hc but affect Ku only in a secondary manner. In this regard grain boundary separation provides a way to minimize the grain-to-grain magnetic coupling which is known to result in larger coercivities and improved SNR as has been discussed extensively in the literature for conventional longitudinal recording media.We present here results from the deposition of two Pt/Co/Tb multilayers (A and B) which show significant differences in their coercive fields.

Imaging magnetic microstructure with SEMPA

1993 ◽  
Vol 51 ◽  
pp. 1032-1033
Author(s):  
M. H. Kelley ◽  
J. Unguris ◽  
R. J. Celotta ◽  
D. T. Pierce
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Scanning Electron Microscopy ◽  
Sandwich Structure ◽  
Magnetic Coupling ◽  
Polarization Analysis ◽  
Secondary Electrons ◽  
Magnetic Microstructure ◽  
Escape Depth ◽  
Scanning Electron

By measuring the spin polarization of secondary electrons generated in a scanning electron microscope, scanning electron microscopy with polarization analysis (SEMPA) can directly image the magnitude and direction of a material’s magnetization. Because the escape depth of the secondaries is only on the order of 1 nm, SEMPA is especially well-suited for investigating the magnetization of ultra-thin films and surfaces. We have exploited this feature of SEMPA to study the magnetic microstrcture and magnetic coupling in ferromagnetic multilayers where the layers may only be a few atomic layers thick. For example, we have measured the magnetic coupling in Fe/Cr/Fe(100) and Fe/Ag/Fe(100) trilayers and have found that the coupling oscillates between ferromagnetic and antiferromagnetic as a function of the Cr or Ag spacer thickness.The SEMPA apparatus has been described in detail elsewhere. The sample consisted of a magnetic sandwich structure with a wedge-shaped interlayer as shown in Fig. 1.

Three-Dimensional Reconstruction of Native Androctonus Australis Hemocyanin

1990 ◽  
Vol 48 (1) ◽  
pp. 452-453
Author(s):  
Nicolas Boisset ◽  
Jean-Christophe Taveau ◽  
Jean Lamy ◽  
Terence Wagenknecht ◽  
Michael Radermacher ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Body ◽  
Body Surface ◽  
Three Dimensional ◽  
Staining Technique ◽  
Three Dimensional Reconstruction ◽  
Dimensional Reconstruction ◽  
View Reconstruction ◽  
Surface Representations ◽  
Top View

Hemocyanin, the respiratory pigment of the scorpion Androctonus australis is composed of 24 kidney shaped subunits. A model of architecture supported by many indirect arguments has been deduced from electron microscopy (EM) and immuno-EM. To ascertain, the disposition of the subunits within the oligomer, the 24mer was submitted to three-dimensional reconstruction by the method of single-exposure random-conical tilt series.A sample of native hemocyanin, prepared with the double layer negative staining technique, was observed by transmisson electron microscopy under low-dose conditions. Six 3D-reconstructions were carried out indenpendently from top, side and 45°views. The results are composed of solid-body surface representations, and slices extracted from the reconstruction volume.The main two characters of the molecule previously reported by Van Heel and Frank, were constantly found in the solid-body surface representations. These features are the presence of two different faces called flip and flop and a rocking of the molecule around an axis passing through diagonnally opposed hexamers. Furthermore, in the solid-body surface of the top view reconstruction, the positions and orientations of the bridges connecting the half molecules were found in excellent agreement with those predicted by the model.

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