Unconventional Magnetic and Resistive Hysteresis in an Iodine‐Bonded Molecular Conductor

Abstract

Simultaneous manipulation of both spin and charge is acrucial issue in magnetic conductors.Wereport on astrong correlation between magnetism and conductivity in the iodinebonded molecular conductor (DIETSe) 2 FeBr 2 Cl 2 [DIETSe = diiodo(ethylenedithio)tetraselenafulvalene],w hichi st he first molecular conductor showing al arge hysteresis in both magnetic moment and magnetoresistance associated with as pin-flop transition. Utilizing am ixed-anion approach and iodine bonding interactions,wetailored amolecular conductor with random exchange interactions exhibiting unforeseen physical properties.

Use of Halogen Bonding in a Molecular Solid Solution to Simultaneously Control Spin and Charge

“…With increasing Br content x, the SDW transition is suppressed and metallic behaviors are maintained down to 1.9 K in the GaBr 4 salt. 40,54 The temperature−Br-content (T−x) phase diagram (Figure 2c) clearly shows the SDW phase shrinks with increasing x. It indicates Br substitution suppresses the nesting instability of Q1D Fermi surfaces by increasing the Fermi surface warping, in other words, enhancing the dimensionality of π electrons, which is quite similar to the application of pressure.…”

“…It indicates Br substitution suppresses the nesting instability of Q1D Fermi surfaces by increasing the Fermi surface warping, in other words, enhancing the dimensionality of π electrons, which is quite similar to the application of pressure. 41,42,54,55 Such a SDW suppression is also observed in the Fe salts (Figure 2b,d). By comparing previous high pressure studies, 41,55 we estimated the chemical pressure by Br substitution.…”

“…The b-axis resistivity is larger by a factor of about 10 4 compared to the a-axis resistivity and coherent transport is observed in this system. [41][42][43]54,55 The b-axis resistivity seems tougher against microcracks by cooling than the a-axis resistivity, especially in the case of mixed salts. To prevent microcracks from forming, we also applied a moderate hydrostatic pressure (<1.5 kbar) to the crystals at room temperature using a BeCu pressure cell with Daphne 7373 as the pressure medium.…”

“…The temperatures of the resistance anomaly coincide with AF ordering temperatures of d spins from magnetic susceptibility χ (Figure 2d), as discussed below. [40][41][42][43]54,55 The increase in resistance at the Neél temperature T N is associated with reconstruction of the Fermi surface induced by a periodic AF potential of Fe 3+ d spins.…”

“…It is markedly different from the slight increase in T N by applying physical pressure. [41][42][43]54,55 Br has larger electron orbitals (4p) than Cl (3p), which gives more effective interactions. It is also suggested that the energy levels of Br 4p orbitals are closer to those of Fe 3d orbitals than to Cl 3p orbitals, which increases d−p mixing to strengthen magnetic interactions.…”