Fe2Al5 contains a Fe-Al matrix through which are threaded disordered one-dimensional chains of overlapping Al sites. We report magnetic, nuclear-magnetic-resonance (NMR), and specific-heat measurements addressing its magnetic and vibrational properties. The Curie-type susceptibility is found to be due to dilute moments, likely due to wrong-site Fe atoms. 27Al NMR shift and spin-lattice relaxation measurements confirm these to be indirectly coupled through a Ruderman-Kittel-Kasuya-Yoshida-type interaction. Specific-heat results indicate a large density of low-energy vibrational modes. These excitations generate a linear-T contribution to the specific heat, which however freezes out below about 10 K. These results are attributed to the presence of anharmonic vibrational modes associated with the disordered structural chains.
@article{arxiv.1601.07644,
title = {Dilute magnetism and vibrational entropy in Fe2Al5},
author = {Ji Chi and Xiang Zheng and Sergio Y. Rodriguez and Yang Li and Weiping Gou and V. Goruganti and K. D. D. Rathnayaka and Joseph H. Ross},
journal= {arXiv preprint arXiv:1601.07644},
year = {2016}
}