Critical Field Determination in Organic Antiferromagnet F4BImNN

TL;DR

This study determines the critical magnetic fields and Neel temperature of an organic antiferromagnet F4BImNN through magnetic measurements, revealing key parameters of its magnetic phase transition at very low temperatures.

Contribution

It provides the first detailed measurement of critical field parameters and Neel temperature for F4BImNN, combining heat capacity and magnetization data at ultra-low temperatures.

Findings

Zero-field Neel temperature of 0.73 K

Critical fields of 170 Oe (parallel) and 306 Oe (perpendicular)

Interchain exchange interaction of -0.09 K

Abstract

A combination of magnetic heat capacity measurements versus temperature under multiple fixed external fields using a polycrystalline sample, plus easy and hard axis aligned magnetization versus field measurements using a single crystal of the radical 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl) at multiple fixed temperatures below 0.75 K, confirmed a zero-field Neel temperature of TN(0) = 0.73 K, with extrapolated 0 K critical field parameters of Hc(parallel) = 170 Oe and Hc(perpendicular) = 306 Oe. Assuming the previously determined 1D intrachain ferromagnetic exchange interaction of J = +22 K between radicals (Hamiltonian H = -2J {\Sigma}Si . Sj), , the interchain exchange in antiferromagnetic with 2zJinter = -0.09 K.