Comparative study of the magnetic properties of TbFe4Al8 and YFe4Al8 compounds

Abstract ZF-, LF- and TF- μSR-measurements were started with the aim to study the interplay of the R- and Fe-sublattices in establishing the magnetic order by comparing TbFe 4 Al 8 and YFe 4 Al 8 . Comparison of the spin-lattice relaxation rates between the two compounds shows that the fast relaxation visible in TbFe 4 Al 8 arises from the Tb 4f moments and is best fitted with a streched exponential (exp (− λt ) β ). The slowing down of the spin dynamics in Tb with β decreasing from 1 to 1 3 on approaching T N from above, is characteristic for the universal behaviour of a classical spin glass. However, the T -dependence of λ resembles more that of a conventional AF system involving rare earth moments. As neutron diffraction has shown long-range magnetic order sets in immediately below T N . The present experiment suggests that the slowing down of the spin dynamics is governed by competing interactions leading to a wide distribution of time correlations. However, the ensuing frustration does not seem to be strong enough to prevent the onset of long-range magnetic order below T N involving both the Tb and the Fe moments. These results confirm the complex long-range ordering process associated with two distinct order parameters and the simultaneous ordering of the two sublattices found by neutron diffraction.