Absence of ferromagnetism in electron-doped rare-earth manganates, Ln_1−xA_xMnO₃ (x>0.5)

Abstract

In order to explore whether the ferromagnetic metallic state ever occurs in the electron-doped rare-earth manganates, a comparative study of the effects of magnetic fields and of cation substitution in the Mn-site were carried out on hole-doped Pr_0.64Ca_0.36MnO₃ and electron-doped Pr_0.36Ca_0.64MnO₃. Unlike Pr_0.64Ca_0.36MnO₃, which attains a ferromagnetic metallic state under an applied magnetic field or on 3% Ru (Cr³⁺) doping in the Mn-site, Pr_0.36Ca_0.64MnO₃ failed to exhibit ferromagnetism even on applying magnetic field on a Ru-doped sample. A study of La_0.33Ca_0.33Sr_0.34MnO₃ with a larger Mn-O-Mn angle has shown it to be a paramagnetic insulator. This manganate also does not exhibit ferromagnetism on 3% Ru substitution and/or on application of a 12 T magnetic field. The present study establishes the absence of ferromagnetism in electron-doped manganates under all conditions.