Structure, Magnetism and First Principles Modeling of the Na0.5La0.5RuO3 Perovskite

TL;DR

This study synthesizes and characterizes Na0.5La0.5RuO3, revealing its tetragonal structure, magnetic glassy transition, and how cation disorder influences magnetic interactions, supported by first-principles calculations.

Contribution

It provides the first detailed structural and magnetic analysis of Na0.5La0.5RuO3, highlighting the impact of cation disorder on magnetic frustration and local interactions.

Findings

Na0.5La0.5RuO3 is a tetragonal perovskite with random La/Na mixing.

No magnetic order observed down to 1.8 K, but a glassy magnetic transition occurs at 1.4 K.

Cation distribution influences local magnetic exchange interactions.

Abstract

High purity polycrystalline Na0.5La0.5RuO3 was synthesized by a solid state method, and its properties were studied by magnetic susceptibility, heat capacity and resistivity measurements. We find it to be a tetragonal perovskite, in contrast to an earlier report, with random La/Na mixing. With a Curie-Weiss temperature of -231 K and effective moment of 2.74 uB/mol-Ru, there is no magnetic ordering down to 1.8 K. A broad hump at 1.4 K in the heat capacity, however, indicates the presence of a glassy magnetic transition, which we attribute to the influence of the random distribution of Na and La on the perovskite A sites. Comparison to CaRuO3, a structurally ordered ruthenate perovskite with similar properties, is presented. First-principle calculations indicate that the Na-La distribution determines the local magnetic exchange inter-actions between Ru ions, favoring either antiferromagnetic or ferromagnetic coupling when the local environment is Na or La rich. Thus our data and analysis suggest that mixing cations with different charges and sizes on the A site in this perovskite results in magnetic frustration through a balance of local magnetic exchange interactions.