A Magnetic and MÖssbauer Spectral Study of the ${\rm Lu}{({\rm Al}_{1-{\rm x}}{\rm Fe}_{\rm x})}_{2}$ Compounds

We present here a magnetic and ⁵⁷Fe Mossbauer spectral study of the Lu(Al_1-xFe_x)₂ compounds (x=0.50, 0.75, and 1). At relatively high temperatures (T_H ~ 300 K for x=0.75 , and T_H ~ 70 K for x=0.50) a peak is observed in both zero field cooled magnetization, M(T), and low field ac susceptibility versus temperature, chi_ac(T), curves. Irreversible phenomena occur at temperatures below the maxima in M(T), and a clear dependence with the exciting frequency is observed in the chi_ac>(T) curves. Similar behavior is observed at lower temperatures (T_L ~ 45 K for x=0.75, and T_L ~ 10 K for x=0.50); however, the low temperature peak in chi_ac(T) is almost frequency independent. The combined analysis of magnetization data and ⁵⁷Fe Mossbauer spectroscopy suggests that the high temperature process corresponds to the apparition of short-range correlations between the magnetic moments, which lead to the formation of magnetic clusters, whereas the low temperature process corresponds to a freezing of the iron magnetic moments.