2020/01/31 by Daniel Brüning, T. Fröhlich, Tobias Fröhlich +14
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Chemistry #Condensed matter physics #Crystallography #Dielectric #Ferroelectricity #Ground state #Magnetic field #Magnetization #Materials science #Multiferroics #Multiferroics and related materials #Nuclear magnetic resonance #Phase transition #Physical chemistry #Physics #Polarization (electrochemistry) #Polarization density #Pyroelectricity #Quantum mechanics #Solid-state spectroscopy and crystallography #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.102.054413
published as Phys. Rev. B 102, 054413 (2020) · 11 pages, 10 figures
arxiv created 2020/01/31 · openalex created_date 2020/02/07 · openalex publication_date 2020/08/07 · arxiv updated 2020/08/12 · openalex updated_date 2026/08/06
We present a study of the dielectric, structural, and magnetic properties of the multiferroic or linear magnetoelectric substitution series [(NH4)_1\ensuremath-xKx]2[FeCl5(H2O)]. 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\ensuremath≤0.06) to a linear magnetoelectric (x\ensuremath≥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 NH4+ tetrahedra but does not break inversion symmetry in the pure material, while a finite K content causes pyroelectricity.