Thermodynamic properties of the new multiferroic material (NH${}_4$)${}_2$[FeCl${}_5$(H${}_2$O)]

Abstract

(NH${}_4$)${}_2$[FeCl${}_5$(H${}_2$O)], a member of the family of antiferromagnetic $A_2$[Fe$X_5$(H${}_2$O)] compounds ($X$ = halide ion, $A$ = alkali metal or ammonium ion) is classified as a new multiferroic material. We report the onset of ferroelectricity below ~6.9 K within an antiferromagnetically ordered state ($T_N\sim 7.25K$). The corresponding electric polarization can drastically be influenced by applying magnetic fields. Based on measurements of pyroelectric currents, dielectric constants and magnetization we characterize the magnetoelectric, dielectric and magnetic properties of (NH${}_4$)${}_2$[FeCl${}_5$(H${}_2$O)]. Combining these data with measurements of thermal expansion, magnetostriction and specific heat, we derive detailed magnetic field versus temperature phase diagrams. Depending on the direction of the magnetic field up to three different multiferroic phases are identified, which are separated by a magnetically ordered, but non-ferroelectric phase from the paramagnetic phase. Besides these low-temperature transitions, we observe an additional phase transition at ~79 K, which we suspect to be of structural origin.

19 pages, 9 figures

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Cited by in corpus (12)

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• Magnetic-Field-Induced Change of Magneto-Electric Coupling in the in Molecular Multiferroic (ND4)2[FeCl5(D2O)]
• Magnetoelectric properties of $A_2$[FeCl${}_5$(H${}_2$O)] with $A=$ K, Rb, Cs
• Anisotropy study of multiferroicity in the pyroxene NaFeGe${}_2$O${}_6$
• Magnetodielectric coupling in a non-perovskite metal-organic framework
• Magnetoelectric coupling in the mixed erythrosiderite [(NH${}_4$)${}_{1-x}$K${}_x$]${}_2$[FeCl${}_5$(H${}_2$O)]
• Multiple field-induced phases in the frustrated triangular magnet Cs${}_3$Fe${}_2$Br${}_9$
• Magnetic Excitations of the Hybrid Multiferroic (ND4)2FeCl5D2O
• Phase transitions of the ferroelectric $({\mathrm{ND}}_4{)}_2{\mathrm{FeCl}}_5\cdot {\mathrm{D}}_2\mathrm{O}$ under a magnetic field
• Single-crystal investigations on the multiferroic material LiFe(WO${}_4$)${}_2$
• Magnetic phase diagram of $A_2$[FeCl${}_5$(H${}_2$O)] ($A$ = K, Rb, NH${}_4$)
• Multiferroic domain relaxation in (NH4)2[FeCl5(H2O)]