M. Poienar, C. Vecchini, G. Andé, A. Daoud-Aladine, I. Margiolaki, A. Maignan, A. Lappas, L. Chapon, M. Hervieu, F. Damay, and C. Martin
The 4%Cu for Mn substitution in CuMnO2 decreases slightly the lattice parameters, reduces the Jahn−Teller distortion of the MnO6 octahedra, but does not change the temperature dependence of the structure, showing a C2/m to P structural transition (in the vicinity of the magnetic transition temperature). In contrast, the antiferromagnetic structure is strongly modified by the substitution, as a propagation vector k = (0 1/2 0) is evidenced for Cu1.04Mn0.96O2 compared to k = (0 1/2 1/2) for CuMnO2. Consequently, the interplane magnetic coupling (along the c axis) changes from antiferromagnetic in CuMnO2 to ferromagnetic in Cu1.04Mn0.96O2 without change in the antiferromagnetic arrangement of the ferromagnetic chains in the (a,b) plane. The nanostructural study points toward the existence of numerous defects at the nanoscale which justify the modeling of strains used in the refinement of the crystalline structure.