Structural and magnetic properties of Cu substituted manganites studied by EXAFS and dc magnetization measurements

We report extended X-ray absorption fine structure (EXAFS) measurements at the Mn K edge and dc magnetic measurements performed on (La1-xCax)(Mn1-yCuy)O3 samples (x = 0.37 and 0.75 and y = 0.03 or 0.08), thus comparing the effects determined by the partial Mn substitution with Jahn-Teller Cu2+ ions with those induced by the already studied analogous substitution of Mn with non-Jahn-Teller Cr3+. Hence, in the present paper we complete our study on the chemical Mn site substitution influence on the nanoscale phase inhomogeneity characteristic of these strongly correlated electron systems. We observe that the Cu2+ substitution in the two compositions belonging from the opposite sides of the phase diagram determines two very different effects. In the x = 0.37 case it weakens the ferromagnetic ordering thus favouring the antiferromagnetic charge ordered phase component, while in the x = 0.75 one it does not significantly modify the charge ordering already present in the system, differently from what previously observed in presence of non-Jahn-Teller Cr3+ substitution.