Highly cation-deficient manganese perovskite, La 1− xMn 1− yO 3 with x= y

Abstract

Oxidative ( δ>0) nonstoichiometry in the perovskite ‘LaMnO 3+ δ ’ has been known to be manifested not with O interstitials but rather with cation vacancies of equal amounts at the two cation sites, La and Mn, i.e. La 1− x Mn 1− y O 3 with x= y. Here, we report the fabrication of samples with record-high cation-vacancy concentrations ( x>0.12 or δ>0.4) by means of a variety of high-pressure oxygenation techniques. Linear (negative) dependence of the cell volume on x was observed within the whole x range investigated, down to 56.9 Å 3 (per formula unit) for a sample oxygenated at 5 GPa and 1100 °C using Ag 2O 2 as an excess oxygen source. With increasing degree of cation deficiency in La 1− x Mn 1− x O 3, the ferromagnetic transition temperature was found to follow a bell shape with respect to x exhibiting a maximum of ∼250 K about x≈0.1. For moderately oxygenated samples large magnetoresistance effect was evidenced.