Magnetic-field-induced ferroelectric states in centrosymmetric ( and Ho)

Abstract

The linear magnetoelectric effect and multiferroicity phenomena occur independently due to breaking inversion symmetry below the magnetically ordered state of either transition metal or rare-earth ions. Here, we report the occurrence of a linear magnetoelectric effect and magnetic field-induced ferromagnetism and ferroelectricity below in the orthorhombic green phases ( and Ho). They undergo a long-range antiferromagnetic ordering of ( and 17.5 K) and ions ( and ). The neutron diffraction study reveals that these compounds undergo a first-order magnetic transition from the high-temperature centrosymmetric antiferromagnetic phase () to the low-temperature noncentrosymmetric phases (Dy) and (Ho), which allow linear magnetoelectric coupling. This is consistent with field-induced electric polarization, below , which varies linearly up to ∼1.2 T. Above a critical field , both compounds exhibit metamagnetic transitions with magnetization close to the saturation value (Dy) and (Ho) at 7 T. Above the metamagnetic transition, a new polar state appears with large electric polarization, indicating field-induced ferroelectricity. We discuss the important role of coupling in determining the ground state magnetic structure responsible for the magnetoelectric coupling in both compounds.