Magnetoelectric Measurement of Magnetite (Fe₃O₄) at Low Temperatures and Direct Evidence for Nonexistence of<i>a</i><i>c</i>Mirror Plane

Abstract

The magnetoelectric (ME) effect was measured for a single crystal of magnetite below 30 K by means of an alternating current (AC) method. The ME domains were controlled through uniaxial mechanical stress together with a magnetic and an electric field. The ME polarization parallel to the b axis induced by rotating the DC magnetic field in the a c plane was successfully reversed upon reversing the electric field applied parallel to the b axis. This is direct evidence that the spontaneous electric polarization has the b axis component, and consequently, the a c mirror plane does not exist.