Abstract
The new paramagnetic molecular superconductor ET4[(H3O)Fe(C2O4)3]·C6H5Br (1) (Tc = 4.0 K) contains layers of superconducting ET donors alternating with paramagnetic hexagonal layers formed by (H3O)+, [Fe(C2O4)3]3− and guest C6H5Br molecules located in the hexagonal cavities. Conductivity measurements show metallic behavior from room temperature with a minimum in the resistivity at ca. 50 K followed by a smooth increase and a sharp drop in the resistivity with an onset at 4.0 K and a zero resistance at ca. 1.0 K. Magnetoresistance measurements indicate that Hc1 is about 7 mT and that Hc2 is very anisotropic (Hc2⊥ ≥ 5.5 T and Hc2|| ≈ 0.5 T). Magnetic susceptibility measurements show the expected paramagnetic behavior of the high spin S = 5/2 Fe(III) ions and an extra temperature independent paramagnetism (Pauli-type) typical of metallic systems. Low field DC and AC magnetic measurements show the expected Meissner effect below ca. 3.5 K and confirm the value of Hc1 obtained from magnetoresistance measurements. X and Q-band ESR spectra show a dysonian narrow line coming from the conducting sublattice plus 5 lines from the [Fe(C2O4)3]3− anion, as expected for an S = 5/2 ground spin state with low ZFS. Heat capacity measurements also confirm the superconducting transition at low temperatures and show a broad transition at higher temperatures that can be attributed to an order–disorder transition of some of the terminal ethylene groups of the ET molecules.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call