Role of calcium ions as doped-hole attractors in destabilizing charge-ordered states in Mn perovskites

Abstract

Magnetization and resistivity measurements have been performed in $({\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{)}_z{\mathrm{MnO}}_{3-\delta }$ perovskites as a function of x, z, and δ around the charge-ordered state. Fifty percent of Ca ions stabilize the charge-ordered state even for ${\mathrm{Mn}}^{4+}$ as low as 40% whereas reducing that impurity concentration to 35% results in a conducting ferromagnetic state even for 50% of ${\mathrm{Mn}}^{4+}$ ions. A model is proposed in which Ca ions act not only as suppliers of holes but as attractors of doped-in holes.