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Energy anisotropy

The direction of the alignment of magnetic moments within a magnetic domain is related to the axes of the crystal lattice by crystalline electric fields and spin-orbit interaction of transition-metal t5 -ions (24). The dependency is given by the magnetocrystalline anisotropy energy expression for a cubic lattice (33) ... [Pg.189]

Below a critical size the particle becomes superparamagnetic in other words the thermal activation energy kTexceeds the particle anisotropy energy barrier. A typical length of such a particle is smaller than 10 nm and is of course strongly dependent on the material and its shape. The reversal of the magnetization in this type of particle is the result of thermal motion. [Pg.176]

Magnetic Anisotropy Energy. There are several kinds of magnetic anisotropy energy and perhaps the most weU known is the magnetocrystaUine anisotropy. Only a crystalline soHd has this property because the energy is dictated by the symmetry of the crystal lattice. For example, in bcc Fe, the easy axis is in a (100) direction and in fee Ni, it is in a (111) direction. [Pg.366]

In this paper, we present another application of the semi-relativistic expansion by evaluating the relativistic corrections to the energy up to 1/c and l/c". This gives us explicit correction terms to the usual calculation of anisotropy energy in magnetic systems. [Pg.451]

Definition and Uses of Standards. In the context of this paper, the term "standard" denotes a well-characterized material for which a physical parameter or concentration of chemical constituent has been determined with a known precision and accuracy. These standards can be used to check or determine (a) instrumental parameters such as wavelength accuracy, detection-system spectral responsivity, and stability (b) the instrument response to specific fluorescent species and (c) the accuracy of measurements made by specific Instruments or measurement procedures (assess whether the analytical measurement process is in statistical control and whether it exhibits bias). Once the luminescence instrumentation has been calibrated, it can be used to measure the luminescence characteristics of chemical systems, including corrected excitation and emission spectra, quantum yields, decay times, emission anisotropies, energy transfer, and, with appropriate standards, the concentrations of chemical constituents in complex S2unples. [Pg.99]

Usually, it is assumed that the magnetic anisotropy in nanoparticles is uniaxial with the magnetic anisotropy energy given by the simple expression... [Pg.220]

Even for applied magnetic fields below 1 T, the Zeeman energy may be larger than the anisotropy energy. Above the blocking temperature application of a... [Pg.222]

Figure 3. Assuming log normal particle distributions and an anisotropy energy constant of 1.10 ergs/cm and a o value of 0.25 the above model spectra were generated using a program described elsewhere (22). The average particle size of each distribution used is given at the lower left of each spectrum. Figure 3. Assuming log normal particle distributions and an anisotropy energy constant of 1.10 ergs/cm and a o value of 0.25 the above model spectra were generated using a program described elsewhere (22). The average particle size of each distribution used is given at the lower left of each spectrum.
The measurement of fluorescence lifetimes is an integral part of the anisotropy, energy transfer, and quenching experiment. Also, the fluorescence lifetime provides potentially useful information on the fluorophore environment and therefore provides useful information on membrane properties. An example is the investigation of lateral phase separations. Recently, interest in the fluorescence lifetime itself has increased due to the introduction of the lifetime distribution model as an alternative to the discrete multiexponential approach which has been prevalent in the past. [Pg.232]

For agglomerated structures, the dipolar interaction between two neighboring crystals contributes to the anisotropy energy. This contribution increases when the inter-crystal distance decreases. [Pg.241]

For large super-paramagnetic crystals or for crystals with a very high anisotropy constant (12), the anisotropy energy is larger than the thermal energy, which maintains the direction of the crystal magnetic moment very... [Pg.244]

When the anisotropy energy is large enough it prevents any precession of the magnetic moment of super-paramagnetic crystals. The magnetic fluctuations then arise from the jumps of the moment between different easy directions. The precession prohibition is introduced into the Freed equations in order to meet that requirement every time the electron Larmor precession frequency appears in the equations, it is set to zero 12). [Pg.245]

A quantitative evaluation of the relaxivities as a function of the magnetic field Bo requires extensive numerical calculations because of the presence of two different axes (the anisotropy and the external field axis), resulting in non-zero off-diagonal elements in the Hamiltonian matrix (15). Furthermore, the anisotropy energy has to be included in the thermal equilibrium density matrix. Figures 7 and 8 show the attenuation of the low field dispersion of the calculated NMRD profile when either the crystal size or the anisotropy field increases. [Pg.248]

For USPIO particles containing only one nanomagnet per particle, the main parameters determining the relaxivity are the crystal radius, the specific magnetization and the anisotropy energy. Indeed, the high field dispersion is determined by the translational correlation time t. ... [Pg.254]

The maximum of relaxivity is proportional to the squared saturation magnetization of the crystal. The low field relaxivity depends on the anisotropy, and the presence of a low field dispersion indicates a low anisotropy energy. [Pg.254]

The interplay between the local Pb polarization and B-site ions may be described by a simple model. As discussed above the magnitude of the local off-centering of Pb " ions is always about 0.5 A, and does not depend on the environment. Thus it could be described as a pseudo-spin, and justifies the pseudo-spin model with the dipolar-dipolar interaction and the local anisotropy energy ... [Pg.80]


See other pages where Energy anisotropy is mentioned: [Pg.189]    [Pg.192]    [Pg.192]    [Pg.174]    [Pg.176]    [Pg.366]    [Pg.367]    [Pg.367]    [Pg.369]    [Pg.371]    [Pg.371]    [Pg.394]    [Pg.181]    [Pg.183]    [Pg.519]    [Pg.519]    [Pg.521]    [Pg.221]    [Pg.201]    [Pg.194]    [Pg.239]    [Pg.242]    [Pg.245]    [Pg.247]    [Pg.247]    [Pg.257]    [Pg.258]    [Pg.334]    [Pg.284]    [Pg.81]    [Pg.193]    [Pg.195]   
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Anisotropy energy barrier

Anisotropy energy initial relative

Anisotropy interfacial energy

Antiphase-boundary energies anisotropy

Crystal anisotropy energy

Crystalline anisotropy energy, magnetic

Dispersion energy anisotropy

Grain energies, anisotropy

Influence of surface energy anisotropy

Larger anisotropy energy

Magnetic anisotropy energy

Magnetic anisotropy energy constant

Materials energies, anisotropy

Subband energies anisotropy

Surface energy anisotropy

Surface energy anisotropy in strained materials

Surface energy anisotropy, defined

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