Antiferromagnetic Ordering in the Single-Component Molecular Conductor [Pd(tmdt)2]

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Investigation of single-component molecular conductors and their electronic properties.
• Understanding the interplay between electronic structure, conductivity, and magnetic ordering in metal complexes.

Purpose of the Study:

• To synthesize and characterize the physical properties of [Pd(tmdt)2] crystals.
• To elucidate the electrical and magnetic behaviors of [Pd(tmdt)2] across a range of temperatures.
• To compare the properties of [Pd(tmdt)2] with related molecular systems like [Ni(tmdt)2] and [Pt(tmdt)2].

Main Methods:

• Two-probe electrical resistivity measurements on single crystals.
• X-ray structural analysis using synchrotron radiation at SPring-8 (20-300 K).
• Electron Spin Resonance (ESR) spectroscopy (2.7-301 K).
• Proton Nuclear Magnetic Resonance ((1)H NMR) measurements (2.5-271 K).
• Density Functional Theory (DFT) band structure calculations.

Main Results:

• Room-temperature conductivity of 100 S·cm(-1), indicating semimetallic behavior.
• Transition to narrow-gap semiconducting behavior upon cooling.
• Observed anomalies in X-ray diffraction around 100 K, with no distinct structural changes.
• ESR and NMR data indicate an antiferromagnetic transition around 50 K, with magnetic ordering distributed up to 100 K.
• Significant differences in electrical and magnetic properties compared to [Ni(tmdt)2] and [Pt(tmdt)2].

Conclusions:

• The experimental and theoretical results suggest [Pd(tmdt)2] is an antiferromagnetic Mott insulator with strong electron correlation.
• The observed properties highlight the unique electronic and magnetic characteristics of palladium complexes in this series.
• The findings contribute to understanding the factors governing electronic and magnetic phase transitions in molecular materials.