Magnetic anisotropy and lowfrequency dielectric r

Authors: M Pinterić M Miljak N Biškup O Milat I Aviani S Tomić D Schweitzer W Strunz I Heinen

Publish Date: 2012/08/17

Volume: 11, Issue: 2, Pages: 217-225

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Abstract

We report a detailed characterization of the magnetism and AC transport in single crystals of the organic conductor κBEDTTTF2CuNCN2Cl by means of magnetic anisotropy measurements and lowfrequency dielectric spectroscopy Magnetic anisotropy obeys CurieWeiss law with negative CurieWeiss temperature in the temperature range 300 K70 K An antiferromagnetic transition with concomitant canted antiferromagnetic state is established at 22 K A large hysteresis in the spinflop transition and magnetic field reversal of the weak ferromagnetic magnetization are documented for the first time A broad dielectric relaxation mode of moderate strength Δε ≈ 3 × 103 emerges at 32 K and weakens with temperature The mean relaxation time much larger than that expected for singleparticle excitations is thermally activated in a manner similar to the DC conductivity and saturates below 22 K These features suggest the origin of the broad relaxation as an intrinsic 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 DzyaloshinskyMoriya interaction is taken into account A Debye relaxation with similar temperature dependence was also observed and seems to be related to an additional ferromagneticlike most probably fieldinduced phase We tentatively associate this phase whose tiny contribution was sample dependent with a Cu2+ magnetic subsystem

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