Ru-NMR Studies and Specific Heat Measurements of Bi3Ru3O11 and La4Ru6O19

TL;DR

This study investigates the low-temperature magnetic and electronic properties of Bi3Ru3O11 and La4Ru6O19 using specific heat and Ru-NMR, revealing antiferromagnetic spin fluctuations as a key factor in their behavior.

Contribution

It provides the first detailed NMR and specific heat analysis of these compounds, confirming AF spin fluctuations through self-consistent renormalization theory.

Findings

Presence of antiferromagnetic spin fluctuations at low temperatures

Anomalous temperature dependence of Knight shifts and specific heats

Consistency with self-consistent renormalization theory for 3D itinerant electrons

Abstract

Specific heats measurements and Ru-NMR studies have been carried out for Bi3Ru3O11 and La4Ru6O19, which commonly have three-dimensional linkages of edge-sharing pairs of RuO6 octahedra. The Knight shifts, the nuclear spin-lattice relaxation rates 1/T1 and the electronic specific heats Cel of these systems exhibit anomalous temperature (T) dependence at low temperatures, as was pointed out by Khalifah et al. [Nature 411 (2001) 660.] for the latter system based on their experimental data of the resistivity, magnetic susceptibility and electronic specific heat. Ratios of 1/T1T to the square of the spin component of the isotropic Knight shift, Kspin estimated for these systems at low temperatures suggest that they have antiferromagnetic (AF) spin fluctuations. It is confirmed by the fact that the T-dependences of 1/T1T and Cel/T of the present systems can be explained by the self-consistent renormalization theory for three dimensional itinerant electron systems with AF spin fluctuations. All these results suggest that the AF fluctuations are the primary origin of the characteristics of their low temperature physical behavior.