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Magnetocapacitive effect in spin density wave system (TMTSF)2AsF6

Multiferroics, materials with coupled different types of order, such as electric, magnetic and structural, have raised a lot of interest recently due to the multiple application possibilities. Spin density wave (SDW) systems with their incommensurate antiferromagnetic order [1] and relaxor ferroelectric-like dielectric response [2] seem natural candidates to exhibit such phenomena, as some early results indicate [3]. We have measured the low frequency dielectric response of CDW system (TMTSF)2AsF6 at very low temperatures down to 1.9 K in the magnetic fields up to 8 T. The influence of the magnetic field on the dielectric properties is negligible with the field in the direction of the easy axis b’, while it is important with the field in the direction of the hard axis c*. This effect is the most pronounced at the lowest temperature. As expected [4], at 1.9 K the resistivity increases up to 4 times almost linearly with the field. However, both the amplitude and the relaxation time of the low frequency relaxation process [2] increase for at least an order of magnitude. As such increase cannot be explained by free carrier screening only, we conclude that the magnetic field has to influence the SDW state directly as well. In addition, our results indicate the existence of the phase transition at 2.1 K [3], and the increase of the SDW glass transition temperature [5] with the magnetic field. [1] W.M. Walsh et al., Phys. Rev. Lett. 45, 829 (1980) ; J.C. Scott et al., ibid. 45, 2125 (1980) [2] F. Nad’, P. Monceau, K. Bechgaard, Solid State Commun. 95, 655 (1995) [3] J. L. Musfeldt, M. Poirier, P. Batail, C. Lenoir, Phys. Rev. B 52, 15983 (1995) [4] P. M. Chaikin, P. Haen, E. M. Engler, R. L. Greene, Phys. Rev. B 24, 7155 (1981) [5] J. C. Lasjaunias, et al, Phys. Rev. Lett. 72, 1283 (1994)

multiferoics; charge density wave; charge density wave

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