Electrical and thermal transport in van der Waals magnets 2H-M$_x$TaS$_2$ (M = Mn, Co)

TL;DR

This study investigates how intercalating Mn and Co atoms into 2H-TaS2 affects its electrical, thermal, and magnetic properties, revealing diverse magnetic phases and transport behaviors linked to the intercalation level.

Contribution

It provides a detailed analysis of magnetic and transport property evolution in 2H-M$_x$TaS$_2$ due to intercalation, highlighting new magnetic phases and multi-band effects.

Findings

Intercalation induces different magnetic anisotropies and phases.

Transport properties show metallic behavior with sign changes in thermopower.

Magnetic transitions are linked to anomalies in resistivity, thermal conductivity, and Hall effect.

Abstract

We report a detailed study of electrical and thermal transport properties in 2H-M$_x$TaS$_2$ (M = Mn, Co) magnets where M atoms are intercalated in the van der Waals gap. The intercalation induces ferromagentism with an easy-plane anisotropy in 2H-Mn$_x$TaS$_2$, but ferromagnetism with a strong uniaxial anisotropy in 2H-Co$_{0.22}$TaS$_2$, which finally evolves into a three-dimensional antiferromagnetism in 2H-Co$_{0.34}$TaS$_2$. Temperature-dependent electrical resistivity shows metallic behavior for all samples. Thermopower is negative in the whole temperature range for 2H-Co$_x$TaS$_2$, whereas the sign changes from negative to positive with increasing Mn for 2H-Mn$_x$TaS$_2$. The diffusive thermoelectric response dominates in both high- and low-temperature ranges for all samples. A clear kink in electrical resistivity, a weak anomaly in thermal conductivity, as well as a slope change in thermopower were observed at the magnetic transitions for 2H-Mn$_{0.28}$TaS$_2$ ($T_\textrm{c}$ $\approx$ 82 K) and 2H-Co$_{0.34}$TaS$_2$ ($T_\textrm{N}$ $\approx$ 36 K), respectively, albeit weaker for lower $x$ crystals. Co-intercalation promoted ferromagnetic to antiferromagnetic transition is further confirmed by the Hall resistivity; the sign change of the ordinary Hall coefficient indicates a multi-band behavior in 2H-Co$_x$TaS$_2$.