The Mössbauer effect provides a unique opportunity to study the local atomic structure and magnetic properties of materials. In crystalline Al-Cu-Fe alloys in particular, this method allows one to study the distribution of iron atoms over different positions in the crystal lattice and their interaction with their immediate environment.
In quasicrystalline Al-Cu-Fe alloys, the Mössbauer effect becomes an even more valuable tool. The absence of strict periodicity in quasi-crystals creates a wide range of local environments for Fe atoms, which is reflected in complex Mössbauer spectra. Analysis of these spectra allows one to obtain information about the types of local symmetry, coordination numbers, and magnetic moments of Fe atoms in various quasi-crystalline positions.
The Mössbauer spectroscopy method using the 57Fe isotope was used to study Al-Cu-Fe alloys of different compositions, prepared by different methods. Ordered and disordered icosahedral phases, as well as rhombohedral crystal structures, were analyzed. The analysis of the spectra showed that the local environment of iron atoms in the studied phases is practically the same. For the icosahedral phase, when the ratio of elements changes, two ways of destabilization of the structure were revealed: the first is characterized by the emergence of a pronounced relationship between the isomer shift and quadrupole splitting, and the second by a decrease in the spread of isomer shift values.
Comparison of data obtained for crystalline and quasicrystalline Al-Cu-Fe alloys allows us to identify the features of the influence of crystalline and quasicrystalline structure on the local environment of iron atoms and their magnetic properties. This, in turn, contributes to a better understanding of the nature of the quasicrystalline state and its differences from the crystalline one.
Author: D. W. Lawther, R. A. Dunlap
Institute: Department of Physics, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada