Pseudo spin

Kind R (2007) Evidence for Ferroelectric Nudeation Centres in the Pseudo-spin Glass System Rbi x(ND4)xD2P04 A 87Rb NMR Study. 124 119-147 Klapotke TM (2007) New Nitrogen-Rich High Explosives. 125 85-121 Kobuke Y (2006) Porphyrin Supramolecules by Self-Complementary Coordination 121 ... 

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 ... 

Evidence for Ferroelectric Nucleation Centres in the Pseudo-spin Glass System Rbi-x(ND4)xD2P04 A RbNMRStudy... 

The onset of FE ordering in D-RADP-30 is shifted down to 80 K. Another feature of this composition is that the FE volume fraction grows much less on lowering the temperature than in D-RADP-0.25 and seems to saturate at 30% for temperatures below 40 K. For ammonium concentrations above about 33% no FE domains or clusters are formed from room temperature down to low temperatures in the pseudo-spin glass D-RADP-x. 

We have demonstrated in this contribution that the structural order-disorder transitions in the KDP family are by far more complex than a pseudo-spin model, for example, could describe. Geometrical constraints and couphng to the soft mode, as well as cluster formation of nanometric size, indicate that here the conventional picture of cooperative phenomena has to be revised. 

We assume that each nucleon has a pseudo-spin i and pseudo-orbital angular momentum k. These couple to form the single particle angular momenta J,J (in [j]) of the two interacting nucleons. The wavefunction of a pair of nucleons coupled to a total angular momentum L (and z component p) is then given by ... 

For this case, dynamic symmetry again yields the same wavefunctions as the SDI, since for i = 1/2, the pseudo-spin is the usual intrinsic spin. We obtain ... 

Disordered systems can be broadly classified into spin glasses, dipolar glasses/pseudo-spin glasses, canonical glasses, conducting polymers (CPs),... 

At lower temperatures, the A - - B and A B intra-H-bond exchange time becomes low on the NMR time scale so that we are in the slow motion regime (Am 1). The deuteron NMR frequency now depends on the instantaneous value of the pseudo-spin S,z... 

Thus, 8 Kb NMR studies on Rb0.4s(ND4)o.55D2P04 reveal that the deuteron "pseudo-spin-glass" transition is just not a simple kinetic slowing down process, but due to a gradual condensation of randomly polarized clusters. The results provide novel information on the temperature dependence and distribution of local RFs and their dynamics. Further, the NMR data suggest that the "pseudospin O-D-O deuteron intra-bond motion determines freezing dynamics. 

The electron Hamiltonian (15) describes the so-called orbital exchange coupling in a three-dimensional (3D) crystal lattice. The Pauli matrices, cr O ), have the same properties as the z-component spin operator with S = As a i) represents not a real spin but orbital motion of electrons, it is called pseudo spin. For the respective solid-state 3D-exchange problem, basic concepts and approximations were well developed in physics of magnetic phase transitions. The key approach is the mean-fleld approximation. Similar to (8), it is based on the assumption that fluctuations, s(i) = terms quadratic in s i) can be neglected. We do not go into details here because the respective solution is well-known and discussed in many basic texts of solid state physics (e.g., see [15]). 

---