GD-155 MOSSBAUER-EFFECT STUDIES AND MAGNETIC-PROPERTIES OF GDFE12-XMOX(N-Y) COMPOUNDS

Structural and magnetic properties of the GdFe12-xMox compounds having the ThMn12 type of structure were studied. Rare-earth nitrides of the composition GdFe12-xMoxNy were prepared by the reaction of GdFe12-xMo x with nitrogen gas at 475 degrees C. The crystal structure and lattic e constants have been determined for all compounds. The lattice expans ion of the nitrogenated compounds is mainly along the alpha-axis, the Curie temperatures are increased by about 110 K. We investigated the e ffect of interstitial nitrogen on the magnetic properties and the Gd-1 55 Mossbauer spectrum of GdFe12-xMox. Values of the electric field gra dient V-zz derived from the quadrupole splitting of the spectra were s trongly negative, with V-zz = -21.3 X 10(21) V m(-2) and V-zz = -19.9 x 10(21) V m(-2) for X = 1.5 and 3.0, respectively. Nitrogenation is s hown to lead to a sign reversal of the 4f as well as of the 3d sublatt ice anisotropies.