Reentrant transition from an incipient charge-ordered state to a ferromagnetic metallic state in a rare-earth manganate

A reentrant transition from an incipient charge-ordered (CO) state to a charge-delocalized ferromagnetic (CDFM) state has been established in the manganate ${\mathrm{Nd}}_{0.25}{\mathrm{La}}_{0.25}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_3,$ in which the average $A$-site ionic radius is 1.19 Å. The reentrant CDFM phase is associated with a first-order phase transition that reduces the orthorhombic distortion of the lattice, in contrast to the CO transition in other manganates where the orthorhombically distorted CO state is stabilized at low temperatures. At the CO-CDFM transition, there is a collapse of the charge-ordering gap as measured by vacuum tunneling spectroscopy.