Incommensurate order

Chen et ai, 2002), which exhibits eight-fold periodicity along the [110] azimuth and incommensurate order along [001] and HBC/Au(lll) (Sellam et ai, 2001) -3 6 ... 

Abstract Electronic correlation effects in La2.ISrINi04 lead to spontaneous phase separation into microscopic spin/charge stripes with commensurate or incommensurate order. Raman scattering experiments on such single crystalline materials show a rich phenomenology of phonon and magnon anomalies due to the new, self-organized periodicities. These effects are observable as function of temperature. 

Christoffersen R., Danes P.K. Structure of commensurate and incommensurate ordered phases in system ZrTi04 - ZrsTi7024. J. Amer. Ceram. Soc. 1992 75 563-69. 

It was first shown by Keeton and Loucks (1968) using relativistic calculations that subtle differences in the Fermi surface between Gd and Dy could be responsible for the occurrence of incommensurate periodic ordering in the latter and likewise in the other lanthanides. These features, shown in fig. 5, consist of webbing betweai the small arms in the AHL plane of the Fermi surface of Dy and yield parallel flat nesting portions of the surface spaced by a -vector q = 2kf,) which correlated with the initial Q of the incommensurate order. The nesting features also give rise to peaks in the generalized susceptibility [eq. (3)] at non-zero q as... 

Fig. 6. Generalized susceptibility functions /(f) for Y, Dy, and Gd showing the pronounced maxima in Dy and Y corresponding to the occurrence of incommensurate magnetic order. Alloys of Gd (see e.g., Wenger 1986) or other rare earths with Y show incommensurate order similar to Dy. The ripples in the Gd function are ascribed to matrix element instaUlities. (After Liu et al. 1971.)...

Such incommensurate ordering is characteristic of the heavy lanthanide elements, terbium to thulium, and is associated with a webbing feature of their... 

Clearly, a, is defined such that a > 0.5 indicates a stronger tendency towards incommensurate ordering and a < 0.5 indicates a stronger tendency towards ferromagnetic ordering. 

A comparison of the polarization curves (positive sweeps) of the ORR on Cu(lll) and Cu(OOl) at the same rotation rate (1600 rpm). Fig. 31, shows relatively small, for example, less than a factor of 2, differences in activity, but very different reaction pathways below —0.4 V. Since very little is known about the nature of adsorbed anions on Cu(hkl) in sulfuric acid solution, or how the adsorption sites might differ between the different surfaces, it is difEcult to rationalize the structural sensitivity of the ORR on Cu hkl). For the Cu(lll)-S04 ad interface, both Wilms and coworkers [102] and li and Nichols [103] found by STM that a complex incommensurate ordered structure of sulfate anions formed at the Cu(lll) surface throughout the —0.1 to —0.4 V potential region in H2SO4. This ordered structure does not appear to lie along any high symmetry directions of the Cu(lll) substrate but it... 

The first evidence for incommensurate smectic modulations was obtained by Leadbetter and coworkers in the smectic E phase of n-alkyl cyanoterphenyls [181, 182]. Subsequent studies presented evidence for fluid SmAi SmA2,i c and SmAinc soliton phases in binary mixtures [183-185]. However, more recent high resolution X-ray studies have contradicted these latter findings and have found that the apparently incommensurate phases are actually coexistence regions between various smectic phases (e.g. SmAi-bSmA SmA2 + SmAd) [24, 186-189]. These authors have recently claimed to have found a true incommensurate ordered smectic phase in mixtures of TBBA and DB6 [190]. Evidence has also been presented for two soli-ton-type incommensurate SmA phases (one... 

Neutron diffraction patterns of annealed NbCx (0.81 S x S 0.88) (4,8) and TaCx (0.79 S X S 0.90) specimens display weak superstructure peaks along with intense structural lines, suggesting an incommensurate ordered phase with a composition close to M Cs (4). The parameter of the fee sublattice of metals for the ordered phase is larger than that for the disordered carbides, indicating that the volume of the crystal varies discontinuously during ordering (4). 

---