Synthesis, composition, and magnetic properties of the ferrimagnetic NdCu 3− xMn 4+ xO 12 perovskite-like phases

Abstract

A magnetic oxide with composition close of NdCu 3Mn 4O 12 with a perovskite-related cubic structure ( a ⋍ 7.30 Å, space group Im3, Z = 2) has been synthesized by using either the high-pressure or the hydrothermal technique. The composition is strongly dependent on the synthesis conditions. A partial reduction of Mn 4+ in the octahedral sites, resulting in a partial substitution of Cu 2+ by Mn 3+ in the Jahn-Teller sites, leads to the actual formula Nd(Cu 2+ 3− x Mn 3+ x )(Mn 4+ 3− x Mn 3+ 1+ x )O 12. For the compound synthesized at 650°C/2 kbar, the value of the substitution parameter x, as determined by neutron diffraction, is 0.32. For samples synthesized at higher temperatures, larger values of x are obtained. The compound is ferrimagnetic with Néel temperature of 390 K and a spontaneous magnetization of 93 emu/g at 4 K (52 emu/g at room temperature). For larger x values, magnetizations up to 118 emu/g at 4 K are obtained.