Nuclear magnetic resonance reveals ‘forbidden’ symmetries in quasicrystals and related metallic alloys with giant unit cells

Abstract

We report on measurements of angular dependences of the selectively excited NMR intensity in a decagonal AlNiCo quasicrystal, icosahedral AlPdMn quasicrystal and orthorhombic ξ′-AlPdMn single crystal with approximately 258 atoms in the unit cell. In all three cases, we found 10-fold rotation patterns, in agreement with structural properties of the investigated samples. However, in the orthorhombic ξ′-AlPdMn complex metallic alloy, a non-perfect 10-fold symmetry was observed, which is a consequence of periodicity that strictly forbids non-crystallographic rotational symmetries. These measurements represent a starting point for testing structural models of quasicrystals and related metallic alloys with giant unit cells by means of NMR.

Acknowledgements

We thank Michael Feuerbacher from Jülich for provision of samples. This research was supported by the Slovenian Research Agency. PJ acknowledges Boehringer Ingelheim Fonds for supplementary support.