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- magneticfield ( 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 k(0) parallel to [ 001]. The B- induced transverse conical spin structure carries the P vector directing perpendicular to both B and k(0), 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.