Resistive properties and phase diagram of the organic antiferromagnetic metalκ−(BETS)2FeCl4

Abstract

The low-temperature electronic state of the layered organic charge-transfer salt κ-(BETS)2FeCl4 was probed by interlayer electrical resistance measurements under magnetic field. Both above and below TN = 0.47 K, the temperature of antiferromagnetic ordering of 3d-electron spins of Fe 3+ localized in the insulating anion layers, a non-saturating linear R(T ) dependence has been observed. A weak superconducting signal has been detected in the antiferromagnetic state, at temperatures ≤ 0.2 K. Despite the very high crystal quality, only a tiny fraction of the sample appears to be superconducting. Besides a small kink feature in the resistivity, the impact of the antiferromagnetic ordering of localized Fe 3+ spins on the conduction π-electron system is clearly manifested in the Fermi surface reconstruction, as evidenced by Shubnikov-de Haas oscillations. The "magnetic field -temperature" phase diagrams for the field directions parallel to each of the three principal crystal axes have been determined. For magnetic field along the easy axis a spin-flop transition has been found. Similarities and differences between the present material and the sister compound κ-(BETS)2FeBr4 are discussed.

Fermi-surface topologies and low-temperature phases of the filled skutterudite compoundsCeOs4Sb12andNdOs4Sb12

“…However, the manner in which the susceptibility contours, and hence the notional L to H phase boundary, curve back towards the origin as the temperature is cooled below 10 K is suggestive of some more complex interplay. Related behavior has been seen in the phase diagrams of reduced-dimensionality antiferromagnets 44,45 ; but by contrast, in those cases, the effect occurred on the high−T , low−H side of the phase boundary and was attributed to the effect of thermal fluctuations on the free energy of the system 44 . In the case of CeOs 4 Sb 12 , the backwards curvature instead occurs in the vicinity of the low-temperature antiferromagnetic state [orange phase boundary in Fig.…”

Interplay between the d - and π -electron systems in magnetic torque of the layered organic conductor κ -(BETS) 2MnVyaselev1, Biberacher2, Kushch3 et al. 2017Phys. Rev. B8180View full textAdd to dashboardCite

“…For example, a considerable π-d coupling in λ-(BETS) 2 FeCl 4 leads to a metal-insulator transition in the π-electron system triggered by an antiferromagnetic (AF) ordering of localized Fe 3+ spins [7] and to a spectacular phenomenon of superconductivity induced by a strong magnetic field [8,9]. In the κ-(BETS) 2 FeX 4 salts the π-d coupling is weaker; however it can be readily traced in a reconstruction of the Fermi surface caused in the AF state [10][11][12], high-field re-entrant superconductivity [13,14], and protection of the low-field superconductivity by the AF ordering [13,15].…”

“…For example, a considerable π-d coupling in λ-(BETS) 2 FeCl 4 leads to a metal-insulator transition in the π-electron system triggered by an antiferromagnetic (AF) ordering of localized Fe 3+ spins [7] and to a spectacular phenomenon of superconductivity induced by a strong magnetic field [8,9]. In the κ-(BETS) 2 FeX 4 salts the π-d coupling is weaker; however it can be readily traced in a reconstruction of the Fermi surface caused in the AF state [10][11][12], high-field re-entrant superconductivity [13,14], and protection of the low-field superconductivity by the AF ordering [13,15].In the present compound the π-d interactions seem to be even weaker. While the metalinsulator transition at T MI ≈ 21 K [1] might, at first glance, appear similar to that in λ-(BETS) 2 FeCl 4 , it is most likely driven by purely the Mott-insulating instability of the π-electron system and not by an AF instability of the localized d-electron spins.…”

Interplay Between Conducting and Magnetic Systems in the Antiferromagnetic Organic Superconductor κ-(BETS)2FeBr4

“…2 (squares). The behaviour resembles that observed on the isostructural sister compound κ-(BETS) 2 -FeCl 4 (κ-Cl salt) at ambient pressure [14]. In the κ-Cl salt this behavior was associated with a spin-flop transition into an intermediate, CAF state.…”

“…Comparing to the present compound, in κ-Cl the CAF phase occupies a significant part of the ambient-pressure phase diagram [14]. The difference stems from different relative contributions of the direct d-d exchange and indirect RKKY exchange, involving the π-d and π-π coupling, in setting the AF order.…”