Magnetoelectric coupling in the mixed erythrosiderite [(NH${}_4$)${}_{1-x}$K${}_x$]${}_2$[FeCl${}_5$(H${}_2$O)]

Abstract

We present a study of the dielectric, structural, and magnetic properties of the multiferroic or linear magnetoelectric substitution series [(NH${}_4$)${}_{1-x}$K${}_x$]${}_2$[FeCl${}_5$(H${}_2$O)]. Pyroelectric currents, magnetic susceptibilities, and thermodynamic properties were examined on large single crystals of the erythrosiderite compounds and detailed magnetic-field versus temperature phase diagrams are derived for three different substitution levels. With increasing potassium concentration the material is tuned from a multiferroic ($x\le 0.06$) to a linear magnetoelectric ($x\ge 0.15$) ground state. In contrast to the respective pure parent compounds with $x=0$ or 1, however, the ferroelectric or linear magnetoelectric polarization in none of the substituted samples is switchable by external electric fields, because these samples exhibit a significant electric polarization already above the magnetic ordering transition. The polarization arises at a higher-lying structural phase transition that is examined by THz spectroscopy and, on a deuterated pure single crystal, by comprehensive neutron-diffraction experiments. The structural phase transition is attributed to an ordering of NH${}_4^{+}$ tetrahedra but does not break inversion symmetry in the pure material, while a finite K content causes pyroelectricity.

11 pages, 10 figures

References in corpus (3)

• Magnetically driven ferroelectric order in Ni${}_3$V${}_2$O${}_8$
• A New Multiferroic Material: MnWO4
• Magnetoelectric properties of $A_2$[FeCl${}_5$(H${}_2$O)] with $A=$ K, Rb, Cs

Cited by in corpus (8)

• Magnetic Excitations of the Hybrid Multiferroic (ND4)2FeCl5D2O
• Inducing ferroelectricity in NH${}_4$I and NH${}_4$Br via partial replacement of protons by deuterons
• Rotational phase transitions in antifluorite-type osmate and iridate compounds
• Ferroelectricity Driven by Orbital Resonance of Protons in CH${}_3$NH${}_3$Cl and CH${}_3$NH${}_3$Br
• Electric Polarization and Magnetic Properties of (NH${}_4$)${}_{1-x}$K${}_x$I (x = 0.05-0.17)
• Multiferroic domain relaxation in (NH4)2[FeCl5(H2O)]
• Magnetic phase diagram of $A_2$[FeCl${}_5$(H${}_2$O)] ($A$ = K, Rb, NH${}_4$)
• Reentrance of spin-driven ferroelectricity through rotational tunneling of ammonium