Properties of Mn2+ and Π-Electron Spin Systems Probed by 1H and 13C NMR in the Organic Conductor κ-(BETS)2Mn[N(CN)2]3

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 disordered tilted structure, which may signify their trend to AF order, frustrated geometrically by the triangular arrangement of Mn in the anion layer. This result suggests that the MI transition in κ-(BETS) 2 Mn[N(CN) 2 ] 3 is not the consequence of the interactions within the Mn 2+ spins but due to the interactions within the π-electron system itself. Vice versa, it is more likely that the disordered tilted structure of the Mn 2+ spins is induced by the ordered π-spins via the π-d interaction.

Spin Vortex Crystal Order in Organic Triangular Lattice Compound

“…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.…”

“…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.…”

Fermi surface properties of the bifunctional organic metal κ−(BETS)2Mn[N(CN)2]Zverev1, Biberacher2, Oberbauer3 et al. 2019Phys. Rev. B8020View full textAdd to dashboardCite

“…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.…”

“…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.…”

Shubnikov–de Haas oscillations and electronic correlations in the layered organic metal κ-(BETS)2 Mn[N(CN)2]3

“…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].…”