Structure magnetic

Ferromagnetic and antiferromagnetic structures can be distinguished by Mossbauer spectra of single-crystal samples in an applied field B. This field B adds to the hyperfine field B, r to give the effective field B, seen in the Mossbauer spectrum as for a ferromagnet and Beir=B Bhf for 

The information contained in the Mossbauer spectrum cannot of itself relate the direction of the magnetic axis to the crystal axes. The spectrum gives information relating the direction of the magnetic axis, via the direction of B, to the principal axis of the electric field gradient and, for 

Ferromagnetic Antiferromagnetic Ferrimagnetic Canted antiferromagnetic (weak ferromagnetic) 

In a similar two-step argument, the orientation of the magnetic axis within a crystal can be deduced via its relation to a Held B applied along a known crystal axis. The addition of the applied and hyperfine fields of the two sublattices of an antiferromagnet gives rise to two values of the effective field, Bi and B2, which are directly seen in the Mossbauer spectrum. The angle a between the antiferromagnetic axis and the applied field direction is obtained from the relation 

In an actual experimental geometry with the single crystal in known orientation to both the gamma-ray beam and the applied field, both the splitting and the relative line intensities combine to fix the angular position of the antiferromagnetic axis. 

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B. Heiiich andJ. A. C. Bland, eds., Eltrathin Magnetic Structures, Spiiugei, Beilin, 1994. 

Losses as caused by its penetration through the magnetic structures (core) and components existing in the vicinity. These losses can be expressed by ... 

These balanced enclosure currents also induce electric fields into nearby structures, RCC beams and columns in the same way as the main conductors, and hence nullify most of the space magnetic fields. These space fields (fields outside the enclosure) are otherwise responsible for causing eddy current and hysteresis losses in the metallic (magnetic) structures, RCC beams and columns in the vicinity. The electrical bonding of enclosures thus... 

The influence of a induced field on a metallic (magnetic) structure is in the form of closed magnetic loops, which cause hysteresis and eddy current losses. These closed loops cannot be broken by insulating magnetic structures at bends or joints or any other locations. (Refer to Figure 28.32 for more clarity.) There is thus no treatment that can be applied to such structures or bodies in the vicinity of an IPB to protect them from the magnetic effects of the field if present in the space. 

Alternatives to XRD include transmission electron microscopy (TEM) and diffraction, Low-Energy and Reflection High-Energy Electron Diffraction (LEED and RHEED), extended X-ray Absorption Fine Structure (EXAFS), and neutron diffraction. LEED and RHEED are limited to surfaces and do not probe the bulk of thin films. The elemental sensitivity in neutron diffraction is quite different from XRD, but neutron sources are much weaker than X-ray sources. Neutrons are, however, sensitive to magnetic moments. If adequately large specimens are available, neutron diffraction is a good alternative for low-Z materials and for materials where the magnetic structure is of interest. 

One further important difference between neutron and X-ray difliaction is the former s sensitivity to magnetic structure. The magnetic moments of neutrons... 

Griinberg, P. (2000) Layered magnetic structures in research and application, Acta Mater. 48, 239. 

It is clear that an ah initio calculation of the ground state of AF Cr, based on actual experimental data on the magnetic structure, would be at the moment absolutely unfeasible. That is why most calculations are performed for a vector Q = 2ir/a (1,0,0). In this case Cr has a CsCl unit cell. The local magnetic moments at different atoms are equal in magnitude but opposite in direction. Such an approach is used, in particular, in papers [2, 3, 4], in which the electronic structure of Cr is calculated within the framework of spin density functional theory. Our paper [6] is devoted to the study of the influence of relativistic effects on the electronic structure of chromium. The results of calculations demonstrate that the relativistic effects completely change the structure of the Or electron spectrum, which leads to its anisotropy for the directions being identical in the non-relativistic approach. 

Though in this paper we have used the relativistic KKR wave functions ets betsis functions, the present approach may be easUy realized within any existing method for calculating the electron states. This will allow the electronic properties of materials with complex magnetic structure to be readily calculated without loss of accuracy. The present technique, being most eflicient for the SDW-type systems, can be also used for helical magnetic structures. In the latter case, however, the spin-polarizing part of potential (18) should be appropriately re-defined. 

It has been shown by several authors that fee iron films exhibit a rich magnetic structure, depending very sensitively on the atomic volume. In particular in Fe... 

P. Griinberg, R. Schreiber, Y. Pang, M.B. Brodsky, and H. Sowers, Layered magnetic structures Evidence for antiferromagnetic coupling of Fe layers across Cr interlayers, Phys. Rev. Lett. 57, 2442 (1986). 

In order to perform the calculation., of the conductivity shown here we first performed a calculation of the electronic structure of the material using first-principles techniques. The problem of many electrons interacting with each other was treated in a mean field approximation using the Local Spin Density Approximation (LSDA) which has been shown to be quite accurate for determining electronic densities and interatomic distances and forces. It is also known to reliably describe the magnetic structure of transition metal systems. 

Schematic representation of the magnetic structure of the Tokamak magnetic confinement device. The lines on the shells represent the direction of the total magnetic field, most of which comes from external coils. The portion that gives the twist, however, comes from current inside the hot plasma itself. The twisting is necessary for stable confinement.

The physical and chemical properties of any material are closely related to the type of its chemical bonds. Oxygen atoms form partially covalent bonds with metals that account for the unique thermal stability of oxide compounds and for typically high temperatures of electric and magnetic structure ordering, high refractive indexes, but also for relatively narrow spectral ranges of transparency. 

We shall illustrate this technique by application to two magnetic structures that exist in nature. Consider the rutile structure associated with the antiferromagnetic crystal MnF2. Figure 12-4 shows the non-... 

Lagrange Multiplier Method for programming problems, 289 for weapon allocation, 291 Lamb and Rutherford, 641 Lamb shift, 486,641 Lanczos form, 73 Landau, L. D., 726,759, 768 Landau-Lifshitz theory applied to magnetic structure, 762 Large numbers, weak law of, 199 Law of large numbers, weak, 199 Lawson, J. L., 170,176 Le Cone, Y., 726... 

Magnetic space groups, 744,758 in describing nonlocalized states, 753 representation of, 742 Magnetic structure application of Landau-Lifshjtz theory, 762... 

Symmetry of magnetic structures, 726 Symmetry properties of eigenstates of a paramagnetic crystal, 745... 

Symmetry used in determining magnetic structure, 758 Synchronization, 372,373 theory by stroscopic method, 375 System function, 181 Systems... 

The rare earths in their dodecaborides have the 3 + oxidation state except for Yb and Tm which have an intermediate valence state. A recoilless y-ray emission spectrum study of TmB,2 shows no magnetic ordering at 1.35 K the spectra of YbB,2 reveal no magnetic structure to 1.35 K. The compounds HoB,2, ErB,2 order antiferromagnetically, and ZrB,2 and LuB,2 become superconducting < 5.8 K and < 0.48 K, respectively. ... 

These limitations, most urgently felt in solid state theory, have stimulated the search for alternative approaches to the many-body problem of an interacting electron system as found in solids, surfaces, interfaces, and molecular systems. Today, local density functional (LDF) theory (3-4) and its generalization to spin polarized systems (5-6) are known to provide accurate descriptions of the electronic and magnetic structures as well as other ground state properties such as bond distances and force constants in bulk solids and surfaces. 

Ovchinnikov, V.V. Mossbauer Analysis of the Atomic and Magnetic Structure of Alloys. Cambridge International Science, Cambridge (2004)... 

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