ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The nature of the interlayer coupling in epitaxial Fe(110)/Ag(111) multilayer structures was investigated using a highly surface-sensitive Mössbauer spectroscopy technique. The films were grown by molecular beam epitaxy and analyzed with x-ray diffraction and in situ RHEED to verify their crystallinity and orientation. All the films took the general form [56Fe3057Fe2Agx]15, where x=3 to 22 monolayers (ML). The entire film is invisible to the Mössbauer effect except for the 2 ML 57Fe layers, which therefore act as a probe of the magnetic environment of the Fe surfaces. Information regarding the surface spin-wave spectrum can then be obtained by measuring the temperature dependence of the hyperfine field at the surface. In the limit of no Ag interlayer, the 57Fe probe layers would be in direct contact with 56Fe on both sides and therefore should display a (1−BT3/2) hyperfine field temperature dependence, with B=5.2×10−6 K−3/2. As the Ag interlayer thickness is increased, we expect the hyperfine field to follow a (1−kBT3/2) temperature dependence, with 1〈k〈3.5 depending on the strength of the interlayer exchange. In addition, we expect an enhancement in H(0), the hyperfine field at 0 K, as the surface exchange decreases. The RHEED and x-ray studies showed all the samples to be single-crystalline and well-oriented, with no Bragg reflections other than Fe(110) and Ag(111) present. As the Ag interlayer thickness increased, the films showed the expected softening of the spin-wave spectrum, with k increasing from 1 at x=0 to 2.2 at x=22. However, a clear oscillation in k was observed at x=6 ML, and a possible second oscillation visible at x=12 ML. This implies an oscillation superimposed upon the monotonically decreasing interlayer exchange. The value of H(0) also shows a similar oscillation at x=6 ML.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.353493
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