Phase transformation and magnetostriction of (R-PR)(Fe-T)(2) (R=Dy, Tb; T=Co, Ni)

Structure and magnetostriction of Dy1-xPrxFe2 (0 less than or equal to x le ss than or equal to 0.5), Dy0.6Pr0.4(Fe1-yTy)(2) (0 less than or equal to y less than or equal to 0.6), and Tb1-zPrz(Fe0.4Co0.6)(2) (0 less than or eq ual to z less than or equal to 1.0) alloys (T=Co, Ni) have been investigate d. It is found that the matrix of the alloys Dy1-xPrxFe2 is a single phase (Dy, Pr)Fe-2 with MgCu2-type structure and the second phase is (Dy, Pr)Fe-3 when x less than or equal to 0.2. The amount of (Dy, Pr)Fe-3 phase increas es with increasing Pr content and becomes the main phase when x=0.4. The ma trix of Dy1-xPrxFe2 is found to be the (Dy, Pr)(2)Fe-17 phase with Th2Zn17- type structure when x=0.5. It is found that the amount of the cubic Laves p hase (Dy, Pr)(Fe, Co)(2) in the Dy0.6Pr0.4(Fe1-yCoy)(2) increases with incr easing Co concentration when 0 less than or equal to y less than or equal t o 0.6. The substitution of Ni for Fe is nearly not favorable for the format ion of the cubic Laves phase (Dy, Pr)(Fe, Ni)(2) in (Dy1-xPrx)Fe-2. The mat rix of (Tb1-zPrz)(Fe0.4Co0.6)(2) is a (Tb, Pr)(Fe, Co)(2) phase with the Mg Cu2-type cubic Laves structure and a second phase of small amount is (Tb, P r)(Fe, Co)(3) phase when z less than or equal to 0.2, z=0.5 and 1.0. When 0 .2<z less than or equal to 0.4, the amount of the (Tb, Pr)(Fe, Co)(3) phase with PuNi3-type structure increases with increasing z and becomes the main phase when z=0.4. When 0.5<z less than or equal to 0.6 the amount of the ( Tb, Pr)(Fe, Co)(3) phase increases sharply, whereas for 0.6<z less than or equal to 0.8 it decreases with increasing z. The polycrystalline magnetostr iction, lambda(parallel to) - lambda(perpendicular to), at room temperature of Dy1-xPrxFe2 exhibits a peak when x=0.3. The lambda(parallel to) - lambd a(perpendicular to) for Dy0.6Pr0.4(Fe1-yMy)(2) (M=Co, Ni) and Tb1-zPrz (Fe0 .4Co0.6)(2) is also examined.