Magnetoelectric properties of A2[FeCl5(H2O)] with A = K, Rb, Cs

The compounds A₂[FeCl₅(H₂O)] with A = K, Rb, Cs are identified as new linear magnetoelectric (non-multiferroic) materials. We present a detailed investigation of their linear magnetoelectric properties through measurements of pyroelectric currents, dielectric constants and magnetization. The anisotropy of the linear magnetoelectric effect of the K-based and Rb-based compound is consistent with the magnetic point group m‧m‧m‧, already reported in literature. A symmetry analysis of the magnetoelectric effect of the Cs-based compound allows us to determine the magnetic point group mmm‧ and to develop a model for its magnetic structure. In addition, magnetic-field versus temperature phase diagrams are derived and compared to the closely related multiferroic (NH₄)₂[FeCl₅(H₂O)].