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Dilute magnetism and vibrational entropy in Fe2Al5

Research paper by Ji Chi, Xiang Zheng, Sergio Y. Rodriguez, Yang Li, Weiping Gou, V. Goruganti, K. D. D. Rathnayaka, Joseph H. Ross

Indexed on: 27 Jan '16Published on: 27 Jan '16Published in: Physics - Materials Science



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.