Top and bottom interfaces in Fe-B multilayers investigated by Mössbauer spectroscopy

Abstract

Mössbauer spectroscopy is frequently applied to gain information on the interfaces in multilayers, and recently the layer sequence permutation of multitrilayers was suggested to enhance its capability to characterize bottom and top interfaces of a given layer. The sequence permutation, however, in the investigated Fe-BAg multitrilayers affected the waviness of the layers as well, and the results hinted at the possibility that although Ag does not mix with Fe and B, the Fe-B amorphous alloy formation is influenced by the layer-sequence-dependent morphology of the Ag layers in the multitrilayers. Now we examine the interface mixing of Fe and B in the case of a fixed layer sequence and varying thickness of the Ag layers in [2 nm B/2 nm Fe/x nm Ag] 4 , 0.2 x 10, multitrilayer samples and in B/Fe/B and B/Fe/Ag trilayers. Below x = 5 nm, both the ratio of the nonalloyed Fe layer and the average hyperfine field of the amorphous Fe-B interface compound change. The variation is attributed to thickness-dependent discontinuities of the Ag layers. Ag acts as a barrier to the diffusion of B from the top side and thus the discontinuities lead to a varying ratio of top and bottom interfaces. The evaluation based on this model shows that the "B on top of Fe" interface has an average B concentration about 11 at. % higher than the "Fe on top of B" interface. A slightly smaller difference, 6 at. %, is deduced from low-temperature conversion electron Mössbauer spectroscopy measurements of the trilayers.

Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

“…The application of this method is limited by the possible mixing and diffusion between the 57 Fe marker and the natural Fe layers, and in case of an extended interface, the quantitative conclusion is difficult. The use of an auxiliary layer prepared from an element non-mixing with iron, e.g., Ag, and the comparison of M/ 57 Fe/M and M/ 57 Fe/ Ag samples-where M can be any kind of material-was suggested recently 16 as a strategy to gain quantitative results on the difference between the top and the bottom Fe interface. The idea is very simple; if the top and the bottom interfaces are similar in an M/Fe/M trilayer, then the hyperfine parameters of the respective spectral component remain unaltered and the intensity of the interface sub-spectrum is halved when the top M layer is replaced by Ag.…”

Extracting the composition of nanocrystals of mechanically alloyed systems using Mössbauer spectroscopy

“…It can be observed that the sextet ascribed to the -Fe type phase continuously broadens as milling time increases due to the progressive formation of the supersaturated bcc Fe(Nb,B) solid solution and to a reduction of the crystal size, as will be described below. Fitting of complex spectra as those studied here is not free from ambiguities [3,33]. HFDs have been used for all the studied milling times.…”

Magnetic Structure and Strain State in Fe/V Superlattices Studied by 57Fe+ Emission and Conversion Electron Mössbauer Spectroscopy

“…Conversion Electron Mössbauer Spectroscopy (CEMS) has been used to study the magnetic properties of the Fe-superlattice systems at the monolayer level enhanced with the 57 Fe + Mössbauer isotopes [4,5,12,[14][15][16]. It was reported that Fe-layers of thickness ≤5 MLs were non-magnetic [5].…”