Abstract:Properties of the spin systems of the localized 3d Mn 2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS) 2 Mn[N(CN) 2 ] 3 were accessed using 1 H and 13 C NMR in order to find their relation to the metal-insulator transition which occurs at ∼23 K. The transition of the system into the insulating state is shown to be followed by localization of the π spins into a long-range ordered staggered structure of AF type. In contrast, the 3d Mn 2+ electron spin moments form a diso… Show more
“…Magnetic order in the BETS layer onsets at T N ∼ 22 K in conjunction with a metal-insulator transition (MIT). This transition is marked by a significant broadening of the 13 C NMR resonances [27,28] and the appearance of a field-induced spin reorientation detected via magnetic torque [26,29]. However, as we elaborate in this work, the angle-dependence of the torque and specific pattern of NMR resonances are incompatible with conventional collinear magnetic orders.…”
mentioning
confidence: 75%
“…In this letter, we consider the magnetic ground state of κ-(BETS) 2 Mn[N(CN) 2 ] 3 (κ-Mn) [22][23][24][25][26][27][28][29][30], which we demonstrate to lie in a parameter region conducive to chiral magnetic order. This material has a layered structure (Fig.…”
Organic salts represent an ideal experimental playground for studying the interplay between magnetic and charge degrees of freedom, which has culminated in the discovery of several spin-liquid candidates, such as κ-(ET)2Cu2(CN)3 (κ-Cu). Recent theoretical studies indicate the possibility of chiral spin liquids stabilized by ring-exchange, but the parent states with chiral magnetic order have not been observed in this material family. In this work, we discuss the properties of the recently synthesized κ-(BETS)2Mn[N(CN)2]3 (κ-Mn). Based on analysis of specific heat, magnetic torque, and NMR measurements combined with ab initio calculations, we identify a spin-vortex crystal order. These observations definitively confirm the importance of ring-exchange in these materials, and support the proposed chiral spin-liquid scenario for triangular lattice organics.
“…Magnetic order in the BETS layer onsets at T N ∼ 22 K in conjunction with a metal-insulator transition (MIT). This transition is marked by a significant broadening of the 13 C NMR resonances [27,28] and the appearance of a field-induced spin reorientation detected via magnetic torque [26,29]. However, as we elaborate in this work, the angle-dependence of the torque and specific pattern of NMR resonances are incompatible with conventional collinear magnetic orders.…”
mentioning
confidence: 75%
“…In this letter, we consider the magnetic ground state of κ-(BETS) 2 Mn[N(CN) 2 ] 3 (κ-Mn) [22][23][24][25][26][27][28][29][30], which we demonstrate to lie in a parameter region conducive to chiral magnetic order. This material has a layered structure (Fig.…”
Organic salts represent an ideal experimental playground for studying the interplay between magnetic and charge degrees of freedom, which has culminated in the discovery of several spin-liquid candidates, such as κ-(ET)2Cu2(CN)3 (κ-Cu). Recent theoretical studies indicate the possibility of chiral spin liquids stabilized by ring-exchange, but the parent states with chiral magnetic order have not been observed in this material family. In this work, we discuss the properties of the recently synthesized κ-(BETS)2Mn[N(CN)2]3 (κ-Mn). Based on analysis of specific heat, magnetic torque, and NMR measurements combined with ab initio calculations, we identify a spin-vortex crystal order. These observations definitively confirm the importance of ring-exchange in these materials, and support the proposed chiral spin-liquid scenario for triangular lattice organics.
“…Indeed, the magnetoresistance, especially in the interlayer direction, may be sensitive to the magnetic state of Mn 2+ ions in the anion layer. The ambient-pressure magnetic experiments [16][17][18] have revealed a dramatic slowing of the spin dynamics in the manganese subsystem at low temperatures and considerable interactions with antiferromagnetically ordering π -electron spins in the Mott-insulating state. However, at present we do not have enough data to establish a direct link between the magnetoresistance behavior and magnetic properties.…”
Section: B Angle-dependent Magnetoresistance and The Fermi Surface Gmentioning
confidence: 99%
“…In the present material this coupling seems to be considerably weaker. It has been found to cause changes of magnetic properties of the Mn 2+ subsystem upon entering the insulating state [16][17][18]. However, no evidence of its influence on the conducting system has been reported so far.…”
We present detailed studies of the high-field magnetoresistance of the layered organic metal κ-(BETS) 2 Mn-[N(CN) 2 ] 3 under a pressure slightly above the insulator-metal transition. The experimental data are analyzed in terms of the Fermi surface properties and compared with the results of first-principles band structure calculations. The calculated size and shape of the in-plane Fermi surface are in very good agreement with those derived from Shubnikov-de Haas oscillations as well as the classical angle-dependent magnetoresistance oscillations. A comparison of the experimentally obtained effective cyclotron masses with the calculated band masses reveals electron correlations significantly dependent on the electron momentum. The momentum-or band-dependent mobility is also reflected in the behavior of the classical magnetoresistance anisotropy in a magnetic field parallel to layers. Other characteristics of the conducting system related to interlayer charge transfer and scattering mechanisms are discussed based on the experimental data. Besides the known high-field effects associated with the Fermi surface geometry, new pronounced features have been found in the angle-dependent magnetoresistance, which might be caused by coupling of the metallic charge transport to a magnetic instability in proximity to the metal-insulator phase boundary.
“…The electrical conductivity is provided by delocalized π electrons of fractionally charged BETS donors arranged in two-dimensional (2D) sheets, whereas magnetic * mark.kartsovnik@wmi.badw.de properties are dominated by localized d-electron spins of Mn 2+ in the insulating anionic layers [18]. In addition to the interesting, still not understood crosstalk between the two subsystems [19][20][21], the narrow, half-filled conduction band is a likely candidate for a Mott instability [22]. The material undergoes a metal-insulator transition at ≈ 21 K [18,22].…”
We present magnetoresistance studies of the quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. Under a moderate pressure of 1.4 kbar, required for stabilizing the metallic ground state, Shubnikov -de Haas oscillations, associated with a classical and a magnetic-breakdown cyclotron orbits on the cylindrical Fermi surface, have been found at fields above 10 T. The effective cyclotron masses evaluated from the temperature dependence of the oscillation amplitudes reveal strong renormalization due to many-body interactions. The analysis of the relative strength of the oscillations corresponding to the different orbits and its dependence on magnetic field suggests an enhanced role of electron-electron interactions on flat parts of the Fermi surface.
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