Inversion-symmetry breaking in the noncollinear magnetic phase of the triangular-lattice antiferromagnet Cu Fe O 2

Magnetoelectric and magnetoelastic phenomena have been investigated on a frustrated triangular antiferromagnetic lattice in $\mathrm{Cu}\mathrm{Fe}{\mathrm{O}}_{2}$. Inversion-symmetry breaking, manifested as a finite electric polarization, was observed in noncollinear (helical) magnetic phases and not in collinear magnetic phases. This result demonstrates that the noncollinear spin structure plays an important role in inducing electric polarization. Based on these results we suggest that frustrated magnets (often favoring noncollinear configurations) are favorable candidates for a new class of magnetoelectric materials.