Ferromagnetic and Antiferromagnetic States of Mn in Y(Co,Mn)₂

Abstract

Electronic structures of Y₂Co₃Mn and Y₂Co₂Mn₂ with cubic Laves phase structure are calculated by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation, by assuming ordered structures. It is shown by the numerical calculations that both solutions of the ferromagnetic and antiferromagnetic states exist in Y₂Co₂Mn₂, while only the ferromagnetic solution is obtained in Y₂Co₃Mn. The total energy for Y₂Co₂Mn₂ in the antiferromagnetic state is a little lower than that in the ferromagnetic state. These results are consistent with the observed concentration dependence of the bulk magnetic moment in Y(Co,Mn)₂ and also with the observed results for Gd(Co,Mn)₂. Moreover, the theoretical lattice constant for Y₂Co₂Mn₂ in the antiferromagnetic state is considerably larger than that in the paramagnetic state, which suggests the possibility of antiferromagnetic Invar effect.