Effect of copper concentration on atomic site occupation by Fe ions and magnetic properties of (PrDy)–(FeCo)–B alloys

The effect of small copper additions (to $\sim$6 at%) on the distribution of iron ions in six crystallographic sites of the unit cell of the main magnetic phase (PrDy)$_{2}$(FeCo)$_{14}$B has been detected. An increase in the copper concentration leads to a decrease in the 8$j_1$ site occupation by iron ions. Independently of the presence of copper, the temperature dependences of the saturation magnetization of all samples have a minimum which can correspond to the presence of a low-temperature phase or a compensation point in grain boundary regions of the (PrDy)$_{2}$(FeCo)$_{14}$ B main magnetic phase. The alloys under study are not additive sets of all phases in their composition, but behave as new materials with the mutual influence of phases on each other.