Magnetic Control of Crystal Chirality and the Existence of a Large Magneto-Optical Dichroism Effect in CuB₂O₄

The possibility of a magnetic field controlling the chirality of matter has been debated for a long time. Here, we report the successful induction of chirality in the noncentrosymmetric canted antiferromagnet, CuB₂O₄, by application of a low intensity static magnetic field. The chirality is reversed by a 90° rotation of the direction of the magnetic field. The induction of chirality by a magnetic field gives rise to a gigantic enhancement of magnetochiral dichroism in this material. The ability to switch handedness in combination with this large magnetochiral optical effect allows us to design new optical devices such as a magnetically controllable isolator.