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  • Magnetic anisotropy and low-frequency dielectric response of week ferromagnetic phase in ▫$\kappa$▫-(BEDT-TTF▫$)_2$▫Cu[N(CN▫$)_2$▫]Cl, where BEDT-TTF is Bis(ethylenedithio)tetrathiafulvalene
    Pinterić, Marko ...
    We report a detailed characterization of the magnetism and AC transport in single crystals of the organic conductor ▫$\kappa$▫-(BEDT-TTF▫$)_2$▫Cu[N(CN▫$)_2$▫]Cl by means of magnetic anisotropy ... measurements and low-frequency dielectric spectroscopy. Magnetic anisotropy obeys Curie-Weiss law with negative Curie-Weiss temperature in the temperature range 300K-70K. An antiferromagnetic transition with concomitant canted antiferromagnetic state is established at 22K. A large hysteresis in the spin-flop transition and magnetic field reversal of the weak ferromagnetic magnetization are documented for the first time. A broad dielectric relaxation mode of moderate strength (▫$\Delta\epsilon\approx 3 \times 10^3$▫) emerges at 32K, and weakens with temperature. The mean relaxation time, much larger than that expected for single-particle excitations, is thermally activated in a manner similar to the DC conductivity and saturates below 22K. These features suggest the origin of the broad relaxation as an intristic property of the weak ferromagnetic ground state. We propose a charged domain wall in a random ferromagnetic domain structure as the relaxation entity. We argue that the observed features might be well described if Dzyaloshinsky-Moriya interaction is taken into account. A Debye relaxation with similar temperature dependence was also observed and seems to be related to an additional ferromagnetic-like, most probably, field-induced phase. We tentatively associate this phase, whose tiny contribution was sample dependent, with a Cu▫$^{2+}$▫ magnetic subsystem.
    Type of material - article, component part
    Publish date - 1999
    Language - english
    COBISS.SI-ID - 4836886