Morphotropic phase transition in alloys of quasi-binary system Er$_{1-x}$Tb$_{x}$Mn$_{2}$

X-ray diffractometry was used to study the morphotropic phase transition in . alloys of the Er$_{1-x}$Tb$_{x}$Mn$_{2}$ system. It has been established that isomorphic substitution of terbium atoms for erbium atoms transforms an Cl4 structure into an C15 structure by generating two types of defects in the hexagonal closepacked structure.