Effect of B and C doping on structure and magnetostriction of high-Pr content alloys

The structure and magnetostriction of the high-Pr content (Tb0.2Pr0.8) (Fe0.4Co0.6)1.88−xC0.05Bx (0 ≤ x ≤ 0.08) alloys homogenized at 700 °C for 7 days have been investigated by X-ray diffraction and magnetic measurement. It was found that the matrix of the (Tb0.2Pr0.8) (Fe0.4Co0.6)1.88−xC0.05Bx alloys belongs to (Tb, Pr) (Fe, Co, C, B)2 phase with MgCu2-type structure. The Curie temperatures are derived from M–T curves, which showed a slight increase when 0 ≤ x ≤ 0.06, then decreases with further increasing x. The composition dependence of magnetostriction λa (= λ∥ − λ⊥) for (Tb0.2Pr0.8) (Fe0.4Co0.6)1.88−xC0.05Bx alloys reaches a maximum value at x = 0.01 at room temperature. The double split (4 4 0) lines of the Laves phase overlap gradually with increasing x and finally approach to form a broadened peak for x = 0.03. The spontaneous magnetostriction λ111 decreases with increasing boron contents.