EFFECTS OF SUBSTITUTIONAL ATOMS ON THE PROPERTIES OF GAMMA'-(FE1-XTMX)(4)N (TM=CO, NI) COMPOUNDS

We report on the influence of substitutional atoms TM (TM = Co, Ni) on the properties of (Fe1-xTMx)(4)N compounds. The structure and magneti c properties were studied by X-ray diffraction, vibrating-sample magne tometer measurement and Mossbauer spectroscopy. All the samples exhibi t a gamma'-Fe4N-type structure. The substitution of Co for iron is ran dom, but Ni has a preference for the corner sites. The hyperfine held and the isomer shift of gamma'-(Fe1-xTMx)(4)N are closely related to t he concentration of the substitutional atom and its site occupation. A ll these can be readily explained by the increase of 3d electrons and the decrease of unit-cell volume. Combining the saturation magnetizati on and the hyperfine field, the magnetic moment of transition-metal at om in gamma'-(Fe1-xTMx)(4)N has been derived. Using high-pressure Moss bauer spectra, the magnetovolume effect and the chemical bonding effec t of the TM atom has been investigated for the first time.