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The Curie temperature of(Nd_(1-x)Pr_x)_2Fe_(14)Co_yB compounds(x=0,0.2,…,1.0 and y=O,2,4,6,14)hasbeen determined with AC initial susceptibility measurement.It was found that the variations of Curie tempera-ture with x is not linear for y=0 and 14,whereas it is linear for other values of y.The lattice constants of(Nd_(1-x)Pr_x)_2Fet_(14)B were determined by using X-ray diffraction.The lattice expansion was mostly along the caxis,whereas that along the a-axis remained practically zero for the whole series.It is suggested that Pr atomsmay show site preference in R_2M_(14)B compounds(M=Fe or Co).Due to the substitution of Co for Fe.thetendency of site preference of Pr becomes less pronounced,which may be attributed to the decrease of differ-ence of crystal electric field(CEF)acting on the two rare earth sites with the introduction of Co or Fe.In con-trast to that of the Pr atoms,the site preference of Co iu(Nd(1-x)Pr_x)_2Fe(14-y)Co_yB compounds does not depend onthe composition of the rare earth sublattice(R=N d or Pr).
The Curie temperature of (Nd_ (1-x) Pr_x) _2Fe_ (14) Co_yB compounds (x = 0,0.2, ..., 1.0 and y = O, 2,4,6,14) has been determined with AC initial susceptibility measurement It was found that the variations of Curie tempera-ture with x is not linear for y = 0 and 14, it it linear for other values of y. The lattice constants of (Nd_ (1-x) Pr_x) _2Fet_ B were determined by using X-ray diffraction. The lattice expansion was mostly along the caxis, and that that along the a-axis remained practically zero for the whole series. It is suggested that Pr atoms show site preference in R_2M_ (14) B compounds (M = Fe or Co) .Due to the substitution of Co for Fe .thetendency of site preference of Pr becomes less pronounced, which may be attributed to the decrease of differ-ence of crystal electric field (CEF) acting on the two rare earth sites with the introduction of Co or Fe.In con-trast to that of the Pr atoms, the site preference of Co iu (Nd (1-x) Pr_x) _2Fe (14-y) Co_yB compounds does not depend on the composition of the ra re earth sublattice (R = N d or Pr).