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 i n the manganate Nd0.25La0.25Ca0.5MnO3, in which the average A-site ion ic radius is 1.19 Angstrom. The reentrant CDFM phase is associated wit h a first-order phase transition that reduces the orthorhombic distort ion of the lattice, in contrast to the CO transition in other manganat es where the orthorhombically distorted CO state is stabilized at low temperatures. At the CO-CDFM transition, there is a collapse of the ch arge-ordering gap as measured by vacuum tunneling spectroscopy.