%e investigated exchange coupling of Fe layers across Au and Cr interlayers by means of light scattering from spin waves. For Au interlayers we find a continuous decrease of this coupling to zero as the Au thickness is increased from 0 to = 20 A. For Cr interlayers of proper thickness we find antiferromagnetic coupling of the Fe layers. In small external fields such double layers order antiparallel with their magnetization perpendicular to the external field, in analogy to the spin-flop phase of antiferromagnets.
The effect of drawing on the structure and molecular orientation of polyamide-6 fibers has
been investigated by 13C solid-state NMR. The molecular orientation in the fibers is determined using a
two-dimensional rotor synchronized magic-angle spinning (MAS) experiment. For the highly oriented
fibers order parameters up to 〈P
6〉 are determined. By using a 13C T1
ρ filter, the orientation in the rigid
(crystalline + rigid amorphous) and mobile (amorphous) regions are separately determined. The orientation
in the rigid phase increases rapidly at low draw ratios up to λ = 3.5 and levels off at higher draw ratios
(〈P
2〉 ≈ 0.75). The mobile amorphous phase remains disordered for low draw ratios but orients rapidly for
draw ratios above λ = 3.5. By using a 13C T1 filter, 13C MAS spectra of the crystalline phase are obtained,
from which the relative amounts of the α- and γ-phase can be quantitatively determined using spectral
deconvolution. It appears that upon drawing the α/γ ratio changes from 60/40 for an undrawn fiber to almost
completely α for a fully drawn fiber. The NMR results are qualitatively supported by wide-angle X-ray
spectroscopy (WAXS) photos.
We study interlayer exchange coupling in epitaxial Fe/Fe(0.56)Si(0.44)/Fe trilayers. Iron-silicide spacers with high structural and compositional homogeneity for thicknesses up to 34 A are grown by coevaporation from two electron-beam sources. The coupling strength oscillates with spacer thickness for temperatures from 20 to 300 K with two antiferromagnetic maxima at 12 and 26 A, and it clearly increases with decreasing temperature down to 80 K. We conclude that the coupling across ordered Fe(1-x)Si(x) ( x approximately 0.5) is described by the conventional theory of interlayer coupling across metallic spacers.
%e investigated exchange coupling of Fe layers across Au and Cr interlayers by means of light scattering from spin waves. For Au interlayers we find a continuous decrease of this coupling to zero as the Au thickness is increased from 0 to = 20 A. For Cr interlayers of proper thickness we find antiferromagnetic coupling of the Fe layers. In small external fields such double layers order antiparallel with their magnetization perpendicular to the external field, in analogy to the spin-flop phase of antiferromagnets.
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