Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln = La, Nd, Sm, Gd)

TL;DR

This study synthesizes and characterizes layered oxy-arsenides LnRuAsO (Ln = La, Nd, Sm, Gd), revealing structural trends, metallic behavior, and magnetic ordering, with insights into anisotropic properties and rare earth magnetism.

Contribution

It provides comprehensive structural, electronic, and magnetic data on LnRuAsO compounds, highlighting trends across the series and differences from Fe analogues.

Findings

Structural trend toward ideal tetrahedral coordination with smaller Ln ions.

Metallic behavior with carrier concentrations of 10^21 - 10^22 electrons/cm^3.

Magnetic ordering of rare earth moments at low temperatures.

Abstract

Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been synthesized and studied using powder x-ray diffraction, electrical transport, magnetization, and heat capacity measurements. Variations in structural properties across the series reveal a trend toward more ideal tetrahedral coordination around Ru as the size of the rare earth element is reduced. The lattice parameters of these Ru compounds show a more anisotropic response to variation in Ln than their Fe analogues, and significant anisotropy in thermal expansion is also observed. Transport measurements show metallic behavior, and carrier concentrations near 10^21 - 10^22 electrons per cm^3 are inferred from simple analysis of Hall effect measurements. Anomalies in resistivity, magnetization, and heat capacity indicate antiferromagnetic ordering of rare earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2 K for NdRuAsO. Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on Ru. Observed behaviors are compared to those reported for similar Fe and Ru compounds.