PbCu3TeO7: An S=1/2 staircase Kagome lattice with significant intra- and inter-plane couplings

TL;DR

This study investigates PbCu3TeO7, revealing complex magnetic behavior with multiple phase transitions and significant intra- and inter-plane couplings that influence its magnetic ordering.

Contribution

The paper provides detailed experimental and theoretical analysis showing that PbCu3TeO7's magnetic properties are affected by strong couplings, deviating from ideal Kagome physics.

Findings

Multiple magnetic anomalies at 36 K, 25 K, and 17 K.

Presence of significant intra- and inter-Kagome couplings.

Long-range magnetic order despite Kagome lattice features.

Abstract

We have synthesized polycrystalline and single crystal samples of PbCu3TeO7 and studied its properties via magnetic susceptibility chi(T) and heat-capacity Cp(T) measurements and also electronic structure calculations. Whereas the crystal structure is suggestive of the presence of a quasi-2D network of Cu2+ (S = 1/2) buckled staircase Kagome layers, the chi(T) data show magnetic anisotropy and three magnetic anomalies at temperatures, TN1 ~ 36 K, TN2 ~ 25 K, TN3 ~ 17 K, respectively. The chi(T) data follow the Curie-Weiss law above 200 K and a Curie-Weiss temperature Theta_CW ~ -150 K is obtained. The data deviate from the simple Curie-Weiss law below 200 K, which is well above TN1, suggesting the presence of competing magnetic interactions. The magnetic anomaly at TN3 appears to be of first-order from magnetization measurements, although our heat-capacity Cp(T) results do not display any anomaly at TN3. The hopping integrals obtained from our electronic structure calculations suggest the presence of significant intra-Kagome (next-nearest neighbor and diagonal) and inter-Kagome couplings. These couplings take the PbCu3TeO7 system away from a disordered ground state and lead to long-range order, in contrast to what might be expected for an ideal (isotropic) 2D Kagome system.