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

铁稀土-铁金属间化合物具有较低的居里温度。居里温度因晶格膨胀而升高。膨胀是由间隙氢、碳和氮获得的。此外，Al或Ga取代Fe使晶格膨胀，居里温度升高。然而，Si取代Fe使居里温度升高，晶格收缩。居里温度的升高不仅仅是晶格膨胀的影响引起的。首席研究员试图分离体积对居里温度的影响。晶格体积是由镥替代钇控制的，Y_<2-x>Lu_xFe_（1-x）<17>。结果表明，该化合物的居里温度存在体积效应，为4.1 × 10^3K/nm^3。Y_2Fe_3的氮化使晶格的体积膨胀<17>为3.35 × 10 ~（-3）<-2>nm^3，居里温度升高400 K，而由体积效应引起的居里温度升高仅为100 K，这说明氮化引起的居里温度升高不能仅用体积效应来解释。在用类金属替代铁提高居里温度的问题上也是同样的情况。Al或Ga替代Fe使居里温度升高，晶格膨胀; Si替代Fe使居里温度降低，晶格收缩。在本研究中，铜替代Fe也会随着晶格收缩而提高居里温度。非磁性元素的替代使晶格膨胀或收缩，从而使居里温度升高。在这项工作中，铌的优先占位进行了研究。结果与Al、Si、Ga的结果相同，说明居里温度的升高不是由于体积效应，而是由于取代基的择优占位作用。

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.