Enhanced stability of charge-order in underdoped Bi0.75Sr0.25MnO3

We report that the charge-ordered phase of Bi0.75Sr0.25MnO3 presents a transition temperature TCO≃600 K, well above the ordering temperature in half-doped Bi0.50Sr0.50MnO3 (TCO≃525 K). Magnetization, calorimetry, and neutron diffraction measurements evidence that, in underdoped Bi0.75Sr0.25MnO3, an off-stoichiometry corresponding to a Mn3+/Mn4+ ratio of 3 increases TCO by ∼75 K with respect to half-doping. This unusual feature confirms the active role of Bi in this family, the only known manganites presenting charge order well above room temperature.