NMR and Mössbauer study of FeAl2

Abstract

We have used NMR and Mössbauer spectroscopy to investigate the magnetism and spin-glass behavior in FeAl2. The results show that the observed behavior can be interpreted as local-moment magnetism residing on the Fe sites. An increase in Fe57 Mössbauer magnetic hyperfine field was observed at the 35−K spin-glass freezing temperature, with a reduced low-temperature value consistent with unquenched fluctuations in the spin-glass state. However, the Al27 NMR shifts and spin-lattice relaxation behavior are consistent with transfer hyperfine interactions to Fe local moments, with a magnitude of approximately 2.5μB. This value is consistent with the bulk magnetization, but surprising compared to other Fe aluminides, given the small Fe−Fe coordination number and associated weakening expected for the magnetic moment.