INVESTIGATION ON MAGNETIC PROPERTIES OF IRON SUBLATTICE IN RARE EARTH IRON INTERMETALLIC COMPOUNDS.

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The iron rare earth-iron intermetallic compound have low Curie temperature. The Curie temperature elevates by expansion of lattice. The expansion was obtained by interstitial hydrogen, carbon and nitrogen. Also substitution of Al or Ga for Fe expanses the lattice and elevation of the Curie temperature was observed. However, the substitution of Si for Fe elevales the Curie temperature with contraction of the lattice. The elevation of the Curie temperature is not caused by the effect of lattice expansion only. The head invesitigator tried to separate the volume effect on the Curie temperature. The lattice volume was controlled by substitution of lutetium for yttrium, Y_<2-x>Lu_xFe_<17>. As the rsults, volume effect on the Curie temperature was obtained for this compound, 4.1x10^3K/nm^3. The volume expansion of lattice by nitorotanation of Y_2Fe_<17> is 3.35x10^<-2>nm^3 and the elvation of the Curie temperature is 400K.The elevation of the Curie temperature expected form the volume effect is only 100K.This result shows that the elevation of the Curie temperature by nitroganation can not explane by volume effect only. It is the same situation on the problem of the Curie temperature elevation by substitution of matalloid for iron. The substitution of Al or Ga for Fe elevates the Curie temperature with expansion of lattice and the substitution of Si for Fe elebates the Curie temperature with contraction of lattice. In this investigation, copper substitution for Fe also elevates the Curie temperature with contraction of lattice. The Curie temperature elevate by substitution of non magnetic elemet with expansion or contraction of lattice. In this work, the preferential site occupation of niobium was studied. The results are the samle as that of Al, Si and Ga.This fact shows the elevation of the Curie temperature is not caused by volume effect but caused by the preferential site occupation of the substituents.