Magnetic properties of the double perovskites LaPbMSbO6 (M = Mn, Co and Ni)

TL;DR

This study synthesized and characterized new double perovskites LaPbMSbO6 (M = Mn, Co, Ni), revealing their monoclinic structure, magnetic transition temperatures, and effects of cation disorder on magnetic properties.

Contribution

It provides detailed structural and magnetic characterization of LaPbMSbO6 double perovskites, including the impact of cation disorder on magnetic transitions.

Findings

All samples are monoclinic with space group P21/n.

Antiferromagnetic transitions occur at low temperatures (8-17 K).

Disorder affects magnetic interactions, especially in LaPbMnSbO6.

Abstract

New double perovskites LaPbMSbO6, where M2+ = Mn2+, Co2+, and Ni2+, were synthesized as polycrystals by an aqueous synthetic route at temperatures below 1000 oC. All samples are monoclinic, space group P21/n, as obtained from Rietveld analysis of X-ray powder diffraction patterns. The distribution of M2+ and Sb5+ among the two octahedral sites have 3% of disorder for M2+ = Ni2+, whereas for M2+ = Mn2+ and Co2+ less disorder is found. The three samples have an antiferromagnetic transition, due to the antiferromagnetic coupling between M2+ through super-superexchange paths M2+ - O2- - Sb5+ - O2- - M2+. Transition temperatures are low: 8, 10 and 17 K for Mn2+, Co2+, and Ni2+ respectively, as a consequence of the relatively long distances between the magnetic ions M2+. Besides, for LaPbMnSbO6 a small transition at 45 K was found, with ferrimagnetic characteristics, possibly as a consequence of a small disorder between Mn2+ and Sb5+. This disorder would give additional and shorter interaction paths: superexchange Mn2+ - O2- - Mn2+.