Possible Localization Behavior of the Inherent Conducting Polymer (CH$_3$)$_{0.9}$ReO$_3$

TL;DR

This study investigates the low-temperature electrical and magnetic properties of poly-MTO, revealing a crossover from metallic to insulating behavior and signs of localization effects in an inherent conducting organometallic oxide.

Contribution

It provides the first resistivity data down to 30 mK for poly-MTO, showing a crossover in conduction behavior and suggesting localization of d$^1$ moments as a key factor.

Findings

Resistivity shows a crossover from metallic to insulating at 30 K.

Resistivity exhibits a logarithmic increase before saturation below 2 K.

Positive linear magnetoresistance observed up to 7 T.

Abstract

Polymeric methyltrioxorhenium (poly-MTO) represents the first example of an inherent conducting organometallic oxide. It adopts the structural motives and transport properties of some classical perovskites in two dimensions. In this study we present resistivity data down to 30 mK which exhibit a crossover from a metallic (d$\rho$/d$T >$ 0) to an insulating (d$\rho$/d$T <$ 0) behavior at about 30 K. Below 30 K an unusual resistivity behavior, similar to that of some doped cuprate systems, is observed: initially the resistivity increases approximately as $\rho \sim$ log$(1/T$) before it starts to saturate below 2 K. Furthermore, a linear positive magnetoresistance is found (up to 7 T). Temperature dependent magnetization and specific heat measurements in various magnetic fields indicate that the unusual resistivity behavior may be driven by spatial localization of the d$^1$ moments at the Re atoms.