EFFECT OF NITROGEN AND METHANE ON THE STRUCTURAL AND MAGNETIC-PROPERTIES OF RFE2 (R = Y, TB AND DY)

Rare-earth iron alloys (R = Y, Tb, and Dy) with the MgCu2 type crystal structure have been prepared and the effect of heat treatment in meth ane and nitrogen gas has been studied. The structural and magnetic pro perties were characterized by x-my diffraction, and magnetic measureme nts. Samples containing Dy were also characterized by Mossbauer spectr oscopy. For low heat treatment temperatures (250 to 350-degrees-C) C(N ) are absorbed resulting in an increased lattice constant. For interme diate heat treatment temperatures a metastable phase forms in the meth ane heat treated samples which has enhanced hard magnetic properties w ith room temperature coercive fields of 1.4 and 1.1kOe found in coarse powders of Tb-Fe-C and Dy-Fe-C, respectively. For high heat treatment temperatures (above 450-degrees-C) decomposition to RC(RN) and alpha- Fe occurs.