Phenomenological description of doped manganites. Electron bandwidth, crystal local structure and Curie temperature

摘要

La0.7Ca0.3Mn0.95M0.05O3 = Mn, Al, 0.5Al + 0.5In, and In) perovskites (ABO(3)) were studied with x-ray diffraction and AC susceptibility measurements. We provide the phenomenological expressions for the electron bandwidth, W, and Curie temperature, Tc, to describe the variance in these values caused by the change of the degree of doping in the A- position and of the type of dopant in the B-position. The observed decrease in Tc with doping is found to be mostly related to the difference in the electron configuration of Mn3+ ions and dopant M, and partially caused by the change in the local crystal structure because of the difference in the Mn3+ - and M-ion radii.