Spin-glass-like behaviour in the ternary U3Fe4+xAl12−x uranium–iron aluminide

• Published in: Intermetallics 2009-01, Vol.17 (1-2), p.25-31
• Main Authors: Gonçalves, A.P., Waerenborgh, J.C., Gaczyński, P., Noël, H., Tougait, O.
• Format: Article
• Language: English
• ISSN: 0966-9795
• DOI: 10.1016/j.intermet.2008.09.003

The U3Fe4+xAl12-x (0 < x < 0.5) intermetallic was prepared by arc melting, followed by annealing at 850 deg C. This compound crystallizes in the hexagonal Gd3Ru4Al12-type structure (e.g. P63/mmc), with room temperature parameters a = 8.7516(3) A and c = 9.2653(4) A for x = 0. The structure is characterized by planar layers of M3Al4 (M = Gd, U), containing M atoms in a triangular arrangement and forming a distorted Kagome net. Magnetic measurements revealed a spin-glass-type behaviour with a freezing temperature, Tf = 7.9 K. The magnitude of the frequency shift of the freezing temperature is approx 0.03 and a Vogel-Fulcher law is followed with values typical for a spin-glass. 57Fe Mossbauer data show that there is no freezing of the iron magnetic moments directions below Tf, indicating that the origin of the spin-glass-like behaviour is related to topological frustration of the uranium moments.