Low-magnetic-field control of electric polarization vector in a helimagnet

The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of ±30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba₂Mg₂Fe₁₂O₂₂, which shows the helimagnetic spin structure with the propagation vector k₀ parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k₀, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis.