Magnetic properties of TbFe4Al8

We have studied the magnetic properties of the compound TbFe4Al8 on a single crystal and on polycrystalline material. When measured with the field applied along the c-direction, the magnetization is comparatively low. It slightly increases below about 50 K and there is a shallow maximum at about 160 K, a temperature at which earlier Mossbauer spectroscopy has indicated the onset of magnetic ordering of the Fe sublattice, When measured along the basal plane direction, the magnetization is much larger and its temperature dependence is characterized by pronounced thermal history effects. Measurements of the magnetic isotherms at various temperatures show the latter to be due to the occurrence of coercivities that are extremely large at low temperatures but decrease at higher temperatures. These coercivities develop after a field-induced transition, the easy direction of the net magnetization being along the [100] direction. The magnetic properties of the single crystal show marked differences with those of a polycrystalline sample. These differences are discussed in terms of concentration fluctuations. (C) 2000 Elsevier Science B.V, All rights reserved.