Magnetoelectric properties of $A_2$[FeCl${}_5$(H${}_2$O)] with $A=$ K, Rb, Cs

Abstract

The compounds $A_2$[FeCl${}_5$(H${}_2$O)] with $A=$ K, Rb, Cs are identified as new linear magnetoelectric materials. We present a detailed investigation of their linear magnetoelectric properties by 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 $m^{\prime }{m}^{\prime }{m}^{\prime }$, already reported in literature. A symmetry analysis of the magnetoelectric effect of the Cs-based compound allows to determine the magnetic point group $mm{m}^{\prime }$ 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 (NH${}_4$)${}_2$[FeCl${}_5$(H${}_2$O)].

17 pages, 10 figures (updated to the weakly revised version that has been accepted for publication)