Chirality-Dependent Magnetoelectric Responses in a Magnetic-Field-Induced Ferroelectric Phase of Pb(TiO)Cu₄(PO₄)₄

Magnetoelectric multiferroic materials can exhibit a variety of functional properties such as electric field control of magnetization and nonreciprocal electromagnetic responses. Such a magnetoelectric response may be further enriched by the combination of the magnetoelectric order and a peculiar crystallographic order, such as crystal chirality. Recently, it was reported that a chiral-lattice magnet Pb(TiO)Cu₄(PO₄)₄ showing a magnetoelectric quadrupole order in its ground state exhibits anomalous chirality-induced tilt of magnetization vector with respect to an applied magnetic field. In this progress report, additional results that advance the understanding of chirality-induced tilt of magnetization vector are presented. It is found that chirality-induced tilt of the magnetization vector also exists in a magnetic-field-induced ferroelectric (FI-FE) phase of this compound that is stabilized in magnetic fields higher than 16 tesla. The resulting transverse component of the magnetization can be switched with an applied electric field through a polarization reversal. The analysis indicates that this transverse component is as large as ≈0.014 μ_B per f.u, suggesting that the tilting angle of the magnetization in the FI-FE phase is much larger than that in the low-field phase. Also, as another research progress, electric field control of nonreciprocal directional dichroism in the FI-FE phase is demonstrated.