Quasi-one-dimensional exchange interactions and short-range magnetic correlations in CuTeO4

TL;DR

This study investigates the magnetic and structural properties of CuTeO4, revealing quasi-one-dimensional antiferromagnetic correlations, short-range magnetic order, and structural faults, challenging its potential as a cuprate superconductor analog.

Contribution

It provides detailed experimental characterization of CuTeO4's magnetic, thermal, and structural properties, highlighting its short-range magnetic order and structural faults, and discusses implications for superconductivity.

Findings

Quasi-one-dimensional antiferromagnetic correlations with J1=165 K.

Presence of short-range magnetic order with correlation length ~10 Å.

Structural stacking faults and lack of substantive dopability.

Abstract

CuTeO4 has been proposed as a crystallographically distinct, yet electronic structure analog, of the superconducting cuprates. Here, we present detailed characterization of the of the physical properties of CuTeO4 to address this proposal. Fitting of magnetic susceptibility data indicates unexpected quasi-one-dimensional, antiferromagnetic correlations at high temperature, with a nearest neighbour Heisenberg exchange of J1=165(4) K. Low temperature heat capacity measurements reveal a sizable T-linear contribution of $\gamma = 9.58(8) mJ mol^{-1} K^{-2}$, qualitatively consistent with expectations for a S=1/2, uniform, Heisenberg spin chain. Below T ~ 40 K, the susceptibility shows an upturn inconsistent with quasi-one-dimensional behaviour. While heat capacity measurements show no signs of magnetic order down to low temperature, the upturn in the magnetic susceptibility coincides with the emergence of a diffuse peak (centered at |Q| ~ 0.7 Angstrom) in the neutron diffraction data, indicative of persistent, short-range, antiferromagnetic order with a correlation length of $\xi$ = 10.1(9) Angstrom at T = 10 K. The onset of nonlinearity and hysteresis in the isothermal magnetization curves suggest the presence of a small ferromagnetic component. This persistent, short-range order is understood in the context of structural modeling of the x-ray and neutron diffraction data that show the presence of a significant density of stacking faults. No evidence for substantive dopability is observed and CuTeO4 appears qualitatively, to have a larger band gap than predicted by density functional theory. We ascribe this finding to the inductive withdrawal effect from high-valence Te and suggest that superconductivity in the copper tellurates is more likely to be found in compounds with a decreased reductive withdrawal effect from Te.