Tuneability and criticality in a three-dimensional stacked molecular system

Berlie, A.; Terry, I.; Szablewski, M.; Giblin, S.R.

Abstract

With the changing of physical properties through chemical substitution in mind, this work shows the applicability of this approach to organic based spin-Peierls (SP) systems. To demonstrate this we have used a well known system, potassium TCNQ, that undergoes an SP transition at TSP=396 K. Simply substituting protons for fluorine, using TCNQF4, shows a decrease in the coupling strength between TCNQ anions where the spin-Peierls transition is dramatically reduced in temperature, with KTCNQF4 showing a TSP at approximately 160 K, which is due to changes of the electron spin density across the molecule. Muon spin relaxation is a more suitable technique for determining the magnetic properties of these systems and measurements were conducted on both KTCNQ and KTCNQF4 in order to study the behavior of the SP transition. This has highlighted and shown that both transitions exhibit the same behavior and so are indeed similar; however, we have also succeeded in being able to tune the transition. Estimates of the dynamic critical exponents from both samples are obtained from the muon data and are found to be ∼0.33, corresponding to a three-dimensional (3D) antiferromagnetic system implying that spin fluctuations associated with the SP state are correlated not just along stacks of dimerized TCNQ anions. This result extends the understanding of the SP phase transition in the KTCNQ system beyond that determined from purely structural studies.

Citation

Berlie, A., Terry, I., Szablewski, M., & Giblin, S. (2016). Tuneability and criticality in a three-dimensional stacked molecular system. Physical Review B, 93(5), Article 054422. https://doi.org/10.1103/physrevb.93.054422

• Journal Article Type: Article
• Acceptance Date: Dec 16, 2015
• Online Publication Date: Feb 24, 2016
• Publication Date: Feb 24, 2016
• Deposit Date: Mar 2, 2016
• Publicly Available Date: Mar 2, 2016
• Journal: Physical Review B
• Print ISSN: 2469-9950
• Electronic ISSN: 2469-9969
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 93
• Issue: 5
• Article Number: 054422
• DOI: https://doi.org/10.1103/physrevb.93.054422
• Public URL: https://durham-repository.worktribe.com/output/1390331