Magnets frustrated by competing exchange (TbFe6Al6 and ErFe6Al6)

Frustration in the RFe6Al6 intermetallics originates from competition betwe en ferromagnetic inter- and antiferromagnetic intra-sublattice exchange in conjunction with crystallographic disorder of the Fe-Al sublattice. The mu SR data give no indication for the presence of a spin-glass-like state belo w their ferrimagnetic ordering temperature of similar to 340 K. The dominan t feature of frustration observed by mu SR is persistent spin fluctuations well below the ordering temperature. The quasi-static limit is only reached around 50 K, which coincides with the temperature where local magnetizatio n saturates. Furthermore, there is evidence that the magnetic ordering of t he 8j sublattice with its random occupation of Al and Fe ions is retarded. (C) 2000 Elsevier Science B.V. All rights reserved.