NMR Investigation of the Organic Conductor lambda-(BETS)2FeCl4

TL;DR

This study uses proton NMR to investigate the magnetic phases of the organic conductor lambda-(BETS)2FeCl4 at high magnetic field and varying temperatures, revealing details about its paramagnetic and antiferromagnetic states.

Contribution

It provides a preliminary NMR analysis of the magnetic phases of lambda-(BETS)2FeCl4, addressing challenges of small sample size and signal detection.

Findings

NMR spectra obtained for the PM and AFI phases.

Techniques developed to detect signals from tiny samples.

Insights into the magnetic behavior at 9.0 T and low temperatures.

Abstract

The two-dimensional organic conductor lambda-(BETS)2FeCl4 has an unusual phase diagram as a function of temperature and magnetic field that includes a paramagnetic metal (PM) phase, an antiferromagnetic insulating (AFI) phase, and a field-induced superconducting phase [S. Uji, H. Kobayashi, L. Balicas, and James S. Brooks, Adv. Mater. 14, 243 (2002), and cited references]. Here, we report a preliminary investigation of the PM and AFI phases at 9.0 T over the temperature range 2.0-180 K that uses proton NMR measurements of the spectrum, the spin-lattice relaxation rate (1/T1), and the spin echo decay rate (1/T2). The sample is asmall single crystal whose mass is approximately 3 micrograms (approximately 2E16 protons). Its small size creates several challenges that include detecting small signals and excluding parasitic proton signals that are not from the sample [H. N. Bachman and I. F. Silvera, J. Mag. Res. 162, 417 (2003)]. These strategies and other techniques used to obtain viable signals are described.