Synthesis and Properties of BaMTeS (M = Fe, Mn, Zn) and the Disordered Structural Analog BaGe0.5TeS

TL;DR

Researchers synthesized and studied new sulfide-telluride compounds, finding unexpected properties in one that lacks magnetic order and shows a hidden transition.

Contribution

The synthesis and characterization of new BaMTeS compounds and the discovery of a hidden transition in BaFeTeS.

Findings

BaFeTeS shows no magnetic ordering or phase transition between 2 and 300 K.

Mössbauer spectroscopy and electrical resistance data suggest a hidden transition near 200 K in BaFeTeS.

The compounds adopt an orthorhombic Cmcm structure, similar to BaMSO phases.

Abstract

A series of tertiary sulfide-tellurides, BaMxTeS (M = Fe, Mn, Zn, Ge), has been synthesized
by solid-state synthesis. The compounds assume an orthorhombic crystal
structure, described by the Cmcm (No. 63) space group,
and are structural analogs of the BaMSO (M = Co,
Zn) phases. The properties of all four analogs are investigated by
DFT analysis. As only the BaFeTeS analog was prepared as a relatively
pure phase, this homologue was subject to further experimental investigations,
including heat capacity, magnetometry, and Mössbauer spectroscopy.
BaFeTeS exhibits no obvious phase transition between 2 and 300 K,
has no paramagnetic behavior, and lacks long-range magnetic ordering.
However, the Mössbauer spectra, as well as electrical resistance
data, indicate a hidden transition near 200 K that is tentatively
explained by a dynamic charge-density-wave mechanism, based on a resonating
valence bond (RVB) model.

Four isostructural
phases with general compositions BaMTeS (M = Fe,
Mn, Zn) and BaGe0.5TeS have been
synthesized by simple solid-state synthesis. The compounds assume
the crystal structure of BaMSO (M = Co, Zn). The
Fe analog was prepared as a sufficiently pure phase for further analysis
and was found to exhibit an unexpected lack of magnetic ordering,
as well as a Mössbauer spectroscopy anomaly at lower temperatures.

Figures