A-site disorder effects in electron-doped manganite La_0.4Ca_0.6MnO₃

摘要

The A-site disorder effects on the stability of charge-ordered state in electron-doped manganite R_0.4A_0.6MnO₃ (where R = La, Pr, Nd, Sm, and A = Ca, Sr, Ba) are investigated by detailed measurements of transport, magnetism, and specific heat. The robust charge-ordered phase within the prototype sample can be successively suppressed by enhancing the A-site disorder, and finally an atomic-scale spin-glass state is evidenced in the highest disordered sample. However, no ferromagnetic phase can be observed; even the long-range charge-ordered antiferromagnetic phase is fully suppressed, which can be associated with the insufficient e _g electron density in such an electron-doped manganite. This revealing is helpful for understanding the origin of ferromagnetic phase in nano-sized or B-site doped charge-ordered manganites with small e _g electron density.