Effect of gallium on the crystal structure and magnetic properties of PrFe11 − x Ga x C y compounds

Abstract

A homogeneity range of the PrFe11 − xGaxCy phase was determined. As the gallium content increases, the lattice parameters were shown to increase, whereas the Curie temperature decreases; the type of magnetic anisotropy at room temperature is unchanged. In the alloys with x > 3, the transformation of the tetragonal lattice of the compound into an orthorhombic lattice with the axial ratio a/b ≤ 1.006 is observed. This is likely to be caused by the ability of gallium to form covalent bonds. Gallium atoms were found to occupy preferentially 16j2 and 4e2 sites in the orthorhombic lattice of the FePr6.5Ga4.5C compound. The atoms located in the 16j2 sites form wavy chains along the [010] direction of the orthorhombic lattice, whereas the iron atoms located in the 16j1 sites form analogous chains along the [100] direction. Owing to this fact, one of these directions is likely to become an easy axis. The alloy with x= 4.5 has a low coercive force at room temperature; at 114 K, its coercive force is Hc = 42.4 kA/m.