Low-Temperature and Dynamic Magnetism of Highly Frustrated 5d2 Li4MgOsO6 Polymorphs in Comparison with 5d3 Li3Mg2OsO6

TL;DR

This study investigates the low-temperature magnetic behaviors of two highly frustrated osmium-based compounds, revealing spin freezing and glassy-like magnetism, and compares how their crystal structures influence magnetic dynamics.

Contribution

It provides new experimental insights into the magnetic properties of Li4MgOsO6 and Li3Mg2OsO6, highlighting the effects of structural polymorphs on magnetic frustration and dynamics.

Findings

Li3Mg2OsO6 exhibits spin freezing below 12K.

Li4MgOsO6 shows glassy-like magnetism below 2K with partial ordering.

Magnetic behavior varies with crystal symmetry and synthesis conditions.

Abstract

Geometric magnetic frustration (GMF) has attracted substantial interest due to the exotic physics and rich phase diagrams revealed by the cancellation of normally-dominant magnetic interactions, giving impetus for the search for novel frustrated systems, most often based on antiferromagnetic correlations between magnetic ions decorating triangular or tetrahedral lattices. We report here low-temperature magnetic susceptibility and muon spin relaxation results on Li4MgOsO6 and Li3Mg2OsO6, members of the A5BO6 "rock salt ordered" family of frustrated materials. In Li3Mg2OsO6 we find spin freezing below 12K. In Li4MgOsO6, which can crystallize into either orthorhombic Fddd or monoclinic C2/m crystal symmetries depending on synthesis conditions, we find magnetism consistent with glassy-like behavior dominating below 2K, with partial ordering and evidence for dynamics at somewhat higher temperatures.