STRUCTURAL AND MAGNETIC STUDY OF NEW YFE2DX COMPOUNDS (0-LESS-THAN-X-LESS-THAN-OR-EQUAL-TO-3.5)

Deuterium absorption by YFe2 at 408 K allows us to obtain several sing le phase YFe2Dx deuterides for 1.2 less than or equal to x less than o r equal to 2.9. For x=1.2, 1.75 and 1.9, superstructure lines indicate d structural deviations from the ideal C15 cubic structure. For x=2.55 , 2.7 and 2.9 the deuterides were found to crystallize in the C15 type structure. For x greater than or equal to 3 a rhombohedral distortion is observed. These deuterides were studied by neutron diffraction, bu lk magnetic and Fe-57 Mossbauer experiments. The existence of deuterid es with different crystallographic and magnetic structures explains th e existence of two phase regions and several plateau pressures in the isotherms at 373 K and 408 K.