Muon spin relaxation investigation of magnetic ordering in the hybrid organic-inorganic perovskites [(CH3)2NH2]M(HCOO)3, M = Ni,Co,Mn,Cu

First-order structural transition in the multiferroic perovskite-like formate [(CH3)2NH2][Mn(HCOO)3]

In this work we explore the overall structural behaviour of the [(CH3)2NH2][Mn(HCOO)3] multiferroic compound across the temperature range where its ferroelectric transition takes place by means of calorimetry, thermal expansion measurements and variable temperature powder and single crystal X-ray diffraction. The results clearly proof the presence of structural phase transition at Tt ~187 K (temperature at which the dielectric transition occurs) that involves a symmetry change from R-3c to Cc, twinning of the crystals, a discontinuous variation of the unit cell parameters and unit cell volume,…

Measuring Motional Dynamics of (CH$_3$)$_2$ NH$_2^+$ in the Perovskite-Like Metal--Organic Framework [(CH$_3$)$_2$ NH$_2$][Zn(HCOO)$_3$]: The Value of Low-Frequency Electron Paramagnetic Resonance

Dimethylammonium zinc formate (DMAZnF) is the precursor for a large family of multiferroics, materials which display co-existing magnetic and dielectric ordering. However, the mechanism underlying these orderings remains unclear. While it is generally believed that the dielectric transition is related to the freezing of the order-disorder dynamics of the dimethylammonium (DMA+) cation, no quantitative data on this motion are available. We surmise that this is due to the fact that the timescale of this cationic motion is on the borderline of the timescales of experimental techniques used in ear…

Giant Rashba Splitting in CH3NH3PbBr3 Organic-Inorganic Perovskite

As they combine decent mobilities with extremely long carrier lifetimes, organic-inorganic perovskites have opened a whole new field in opto\-electronics. Measurements of their underlying electronic structure, however, are still lacking. Using angle-resolved photoelectron spectroscopy, we measure the valence band dispersion of single-crystal CH$_3$NH$_3$PbBr$_3$. The dispersion of the highest energy band is extracted applying a modified leading edge method, which accounts for the particular density of states of organic-inorganic perovskites. The surface Brillouin zone is consistent with bulk-t…

磁各向异性对[CH$_3$NH$_3$]Fe(HCOO)$_3$基态的影响：对非本征调制磁结构的深入探讨

Influence of Magnetic Anisotropy on the Ground State of [CH$_3$NH$_3$]Fe(HCOO)$_3$: Insights into the Improper Modulated Magnetic Structure

本研究通过结构表征、中子衍射与密度泛函理论计算，揭示了[CH$_3$NH$_3$]Fe(HCOO)$_3$在冷却时经历两次调制波矢变化的无公度结构相变，并在17 K以下形成三维反铁磁有序，其非本征调制磁结构的自旋取向垂直于同类化合物。