Electric polarization induced by transverse magnetic field in the anisotropy-controlled conical helimagnet Ba2(Mg1-xZnx)2Fe12O22

Microscopic origin of magnetic-field (B) induced electric polarization (P) potentially up to near room temperature has been investigated for helimagnets Ba-2(Mg1-xZnx)(2)Fe12O22 with controlled magnetic anisotropy by revealing B- and x-dependent changes of magnetoelectric responses. As Zn concentration (x) increases, the B-induced P rapidly diminishes, accompanying the change in the magnetic-easy surface from conical to planar. Possible spin structures are proposed to explain the observed B dependence of P in terms of the spin-current model. The results indicate the important role of magnetic anisotropy in the B-induced ferroelectric state of this class of helimagnets.