Dilute magnetism and vibrational entropy in Fe2Al5

TL;DR

This study investigates the magnetic and vibrational properties of Fe2Al5, revealing dilute magnetic moments and low-energy vibrational modes linked to disordered chains, with implications for understanding complex metallic alloys.

Contribution

It provides new insights into the dilute magnetism and vibrational entropy in Fe2Al5, highlighting the role of structural disorder and anharmonic vibrations.

Findings

Dilute magnetic moments are likely due to wrong-site Fe atoms.

Presence of low-energy vibrational modes causes linear-T specific heat contribution.

Vibrational excitations freeze out below about 10 K.

Abstract

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.