Magnetic symmetry breaking

For 4t (Uthe relevant perturbation consists in perturbing the covalent (or neutral) VB structures by their interaction with the ionic ones this is the strongly correlated or magnetic domain. So that the Hartree Fock symmetry breaking occurs in a zone which covers the whole magnetic domain and a significant part of the "weakly" correlated domain... 

Fig. 60. The variation of the basal plane cylindrical symmetry breaking magnetoelastic stress, Af p, at 10 K and at an applied magnetic field of 12 T, multiplied by (/iho + nLu)< as a function of n o (where ho and n y are the number of atomic planes in the Ho and Lu blocks, respectively) for (Ho /Lu 15)50 superlattices. The line indicates the fitting by the theoretical model. After Del Moral et al. (1998).

The effect of neutron-proton symmetry breaking on the distribution of M1 strength in the SU(3) limit of the Interacting Boson Model (IBA-2) is studied. A possible alternative choice for the Majorana force is investigated, with a structure that resembles more closely that which is calculated in microscopic theories. It is found that the specific choice for the Majorana interaction has important consequences for the magnetic strength distribution function. In addition it allows for an alternative interpretation of the second excited K7T=0+ band in rare earth nuclei, as a mixed-symmetry state. 

If the quantum corrections to conductivity are actual the magnetoresistance related to the influence of the magnetic field on these corrections takes place [57-59]. The interference of electrons passing the closed part of trajectory in clockwise and counter-clockwise directions causes the so-called corrections to the conductivity. The phases of the electron wave functions in this case are equal and so this interference is constructive. Therefore, the probability for electrons to come back to the initial point doubles. This leads to the interference corrections which increase the classical resistance. The external magnetic field breaks the left-right symmetry, and the phases collected by the electron wave function while it passes trajectory in clockwise and... 

A possible interpretation for the origin of the gap is a commensurate (n, it spin density wave. It induces a symmetry breaking, folding the Fermi surface upon itself, and a partial gap Asdw opens at the intersection of the antiferro-magnetic Brillouin zone, creating pockets in the Fermi surface [5],... 

We have found that in a temperature interval above Tc and below some T 300 K the nuclear spin relaxation for a broad class of cuprates comes from two independent mechanisms relaxation on the stripe -like excitations that leads to a temperature independent contribution to 1 /63i and an universal temperature dependent term. For Lai.seSro.nCuC we obtained a correct quantitative estimate for the value of the first term. We concluded from eq.(l) and Fig.3 that "stripes always come about with external doping and may be pinned by structural defects. We argue that the whole pattern fits well the notion of the dynamical PS into coexisting metallic and IC magnetic phases. Experimentally, it seems that with the temperature decrease dynamical PS acquires the static character with the IC symmetry breaking for AF phase dictated by the competition between the lattice and the Coulomb forces. The form of coexistence of the IC magnetism with SC below Tc remains not understood as well as behaviour of stoichiometric cuprates. 

As far as the continuous symmetry breaking is concerned, the Goldstone theorem states [4] that this will generate hydrodynamic modes, that is, gapless excitations. The order parameter is multicomponent (n > 1) a vector i for magnetism breaking the rotational symmetry, a complex variable i j = ip e/e for charge-density waves and for superconductivity which... 

Electrical and Magnetic Properties of MEM(TCNQ)2 Contrary to TEA(TCNQ)2, the chain structure in MEM(TCNQ)2 [24,25] is found to go discontinously from a very weak dimerization above 335 K to a strong dimerization below 335 K. This is a first-order transition which is reminiscent here of a 4kF transition, although there is still no symmetry breaking [28]. An additional tetramerization also starts to develop continuously below 19 K. This last transition, which now involves symmetry breaking, can be identified with a true second-order 2kF transition [17,18,28] (see Section 7). 

Dei, A., Gatteschi, D., Massa, C. A. etal. (2000) Spontaneous symmetry breaking in the formation of a dinuclear gadolinium semiquinonato complex synthesis, high-field epr studies, and magnetic properties. Chemistry -A European Journal, 6, 4580 586. 

Within the framework of the local density method, which is strictly an orbital theory, the antiferromagnetic state can be attained by reducing the symmetry constraints imposed on spin-polarized calculations, hence allowing the spin orbitals to localize and local magnetic moments to persist, if it is variationally favorable to do so. While I do not know of any formal justification for this type of symmetry breaking (one cannot just mix determinants within DFT to obtain proper spin and space eigenfunctions), the results discussed below for Cr2, M02, and Mn2 certainly indicate that it is a reasonable approach. A rough rationalization can be obtained if one reasons... 

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