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Magnetoelectric effects in single crystals of the cubic ferrimagnetic helimagnet Cu2OSeO3

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posted on 2018-08-07, 12:40 authored by M. Belesi, Ioannis RousochatzakisIoannis Rousochatzakis, M. Abid, U.K. Rossler, H. Berger, J.P. Ansermet
We present magnetodielectric measurements in single crystals of the cubic spin-1/2 compound Cu 2OSeO 3. A magnetic-field-induced electric polarization (P) and a finite magnetocapacitance (MC) is observed at the onset of the magnetically ordered state (T c=59K). Both P and MC are explored in considerable detail as a function of temperature (T), applied field H a, and relative field orientations with respect to the crystallographic axes. The magnetodielectric data show a number of anomalies which signal magnetic phase transitions, and allow us to map out the phase diagram of the system in the H a-T plane. Below the 3-up-1-down collinear ferrimagnetic phase, we find two additional magnetic phases. We demonstrate that these are related to the field-driven evolution of a long-period helical phase, which is stabilized by the chiral Dzyaloshinskii-Moriya term DM•(×M) that is present in this noncentrosymmetric compound. We also present a phenomenological Landau-Ginzburg theory for the magnetic-field-induced electric polarization (ME H) effect, which is in excellent agreement with experimental data, and shows three main features: (i) the polarization P has a uniform as well as a long-wavelength spatial component that is given by the pitch of the magnetic helices, (ii) the uniform component of P points along the vector (HyHz,HzHx,HxHy), and (iii) its strength is proportional to η2-η2/2, where η is the longitudinal and η is the transverse (and spiraling) component of the magnetic ordering. Hence, the field dependence of P provides a clear signature of the evolution of a conical helix under a magnetic field. A similar phenomenological theory is discussed for the MC. © 2012 American Physical Society.



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Physical Review B - Condensed Matter and Materials Physics






BELESI, M. ... et al., 2012. Magnetoelectric effects in single crystals of the cubic ferrimagnetic helimagnet Cu2OSeO3. Physical Review B - Condensed Matter and Materials Physics, 85: 224413.


© American Physical Society (APS)


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This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

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This paper was accepted for publication in the journal Physical Review B - Condensed Matter and Materials Physics and the definitive published version is available at https://doi.org/10.1103/PhysRevB.85.224413






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