Structure and magnetostriction of Nd0.67Tb0.33 (Co1-xFex)2 compounds

The crystal structure, Curie temperature and magnetostriction of compounds with the formula Nd0.67Tb0.33 (Co1-xFex)2 were investigated by x-ray powder diffraction and magnetic measurements. It is revealed that the substitution of Fe for Co destabilizes the cubic Laves phase Nd0.67Tb0.33 (Co,Fe)2. The maximum substitution of Fe for Co is about 0.57. The lattice constant of the Nd0.67Tb0.33 (Co,Fe)2 phase increases with x increasing from x = 0.0 to 0.6, then remains almost unchanged from x = 0.6 to 0.9. The Curie temperature exhibits a variation similar to that of the lattice constant with the Fe concentration. A spin reorientation is observed, which can be understood on the basis of the two-sublattice model. The spontaneous magnetostriction constant λ111 shows a maximum value of 1.7 x 10-3 at x = 0.4. The temperature dependence of λ111 for Nd0.67Tb0.33 (Co0.6Fe0.4)2 exhibits an abrupt jump at 165 K, which corresponds to the temperature of the spin reorientation