CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF THE TERNARY COMPOUND YFE8.6TI1.1 AND ITS HYDRIDE

The occurrence of ternary intermetallic compounds in the Fe-rich corne r of the system Y-Fe-Ti has been studied by X-ray diffraction. It has been shown that, close in composition to the (ThMn12-type) compound YF e11Ti, there exists a further ternary compound having the composition YFe8.6Ti1.1. A structural determination made by means of neutron diffr action showed that it has a defect structure based on the CeMn6Ni5-typ e structure. The Ti atoms are restricted to a single type of site but only half of these sites are occupied. The compound YFe8.6Ti1.1 is non -magnetic. Hydrogen absorption leads to the formation of a hydride of composition YFe8.6Ti1.1H1.2, in which the H atoms show a strong prefer ential occupation of a single type of interstitial site. The hydride o rders ferromagnetically below about 80 K but concentration fluctuation s lead to short-range ordering far above this temperature.