Neutron spin fluctuations

Other possible direct probes are optical experiments similar to studies [113] of vesicles but expanded towards shorter A (20-30 A). Alternatively neutron spin-echo studies of stacked bilayer arrays, which can probe the 10-30 A range [114], might possibly be applicable here. Finally, the x-ray grazing-incidence technique has been shown to be a powerful tool for studying short wavelength fluctuations at fluid interfaces [100]. The application of this technique to the investigation of membrane surface fluctuations can reasonably be expected in the near future [115,116]. 

T.E. Mason, Neutron scattering studies of spin fluctuations in high-temperature superconductors 281... 

Two possibilities are considered for the discrepancy in the amount of the magnetic moment. One is as follows since the observing time of the NMR signal is longer than that of the neutron diffraction, it is considered that rapid spin fluctuations do not contribute to the static moment in NMR experiment. The other possibility is ascribed to a field induced phase transition. In ref. [4] it is reported from the ESR experiment that a phase transition occurs around the applied field of 0.05 T in the temperature region between Tn and T. Since the NMR experiment was performed in an applied field of 0.5 T, the magnetic phase is different from that of the neutron diffraction experiment that was carried at zero magnetic field. 

In this subsection, the theoretical background for SANS and neutron spin-echo measurements carried out with o/w- and w/o-droplet microemulsions will be presented. According to Milner, Safran and others, shape fluctuations in droplet microemulsions can be described in terms of spherical harmonics [42-44]. This offers the possibility to calculate a dynamic structure factor S(q,w) or its Fourier transform, i.e. the intermediate scattering function I(q,t) for the problem, which can be used to analyse dynamical measurements by neutron spin-echo spectroscopy [45]. For the scattering from thin shells I(q,t) was calculated [43]... 

Hellweg, T., Gradzielski, M., Farago, B. and Langevin, D. (2001) Shape fluctuation of microemulsion droplets A neutron spin-echo study. Colloids Surf. A, 183-185, 159-169. 

Oeser, R. et al., 1988. Dynamic fluctuations of crosslinks in a rubber a neutron-spin-echo study. Phys. Rev. Lett. 60, 1041. 

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