NMR and Mössbauer study of spin-glass behavior inFeAl2

Abstract

We have used NMR and Mössbauer spectroscopy to investigate the magnetism and spin-glass behavior in FeAl 2 . The results show that the observed behavior can be interpreted as local-moment magnetism residing on the Fe sites. An increase in 57 Fe 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 27 Al NMR shifts and spin-lattice relaxation behavior are consistent with transfer hyperfine interactions to Fe local moments, with a magnitude of approximately 2.5 B . 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.

Disorder effect on the magnetic behavior of mechanically alloyedFe1−xAlx(0.2Zamora1, Alcázar2, Vélez3 et al. 2009Phys. Rev. B482220View full textAdd to dashboardCite

“…1,2 Experimental and theoretical evidences have established that this anomaly corresponds to a pure SG freezing transition, [4][5][6] which takes place at temperatures near 30 K. For ordered Fe 0.7 Al 0.3 single crystals, this transition was reported to be of the re-entrant spin-glass ͑RSG͒ type with a freezing temperature of ϳ80 K. 7,8 The second phenomenon is the superparamagneticlike ͑SP͒ behavior initially proposed by Cable et al 10 for alloys with a composition around 30 at. % Al.…”

Mössbauer study of incompletely alloyed nanocrystalline Fe100 − x Al x prepared by high energy ball milling

“…Mechanical alloying being a high energy, non-equilibrium process, in addition to producing a high degree of chemical disorder, also introduces defects and strain. These effects result in a larger degree of distortion at 57 Fe sites leading to a larger quadrupole splitting in comparison to the value in an ordered alloy as used by Chi et al [36]. As pointed out earlier, the magnetic hyperfine sextet of the Mössbauer spectra of the as milled samples (Fig.…”

Study of the iron atom clustering in mechanically alloyed Al-rich Fe-Al mixture

“…The magnetism in the nonmagnetic ordered Fe-Al alloy (B2 structure) was induced by the ball milling because of the iron atom clustering on the grain boundaries [9]. Furthermore, a similar low temperature magnetism of Al-rich Fe-Al alloys was also observed for the FeAl 2 intermetallic compound having a more complicated Fe-Al atom ordering where iron atoms have a different number of iron atoms in their neighbourhood [15,16]. Theoretical calculations of the ground state of (FeAl) n (n≤6) clusters revealed that iron atoms cluster due to the domination of Fe-Fe atom interactions [17].…”