Mn Site Substitution Of La0.67Ca0.33MnO3 With Closed Shell Ions: Effect on Magnetic Transition Temperature

Mn site is substituted with closed shell ions (Al, Ga. Ti, Zr and a certain combination of Zr and Al) and also with Fe and Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at. %. Substitution did not change either the crystal symmetry or the oxygen stiochiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures (TP® and TC respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising due to difference in the ionic radii (rMn3±rM) between the substituent (rM) and the Mn3+ ion (rMn3+) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and that of the neighboring Mn ion.