Magnetic order in a metal thiocyanate perovskite-analogue

Metal thiocyanate perovskite-analogues are a growing class of materials, but although they contain paramagnetic cations there have been no reports of their magnetic properties. Due to the large separations between the paramagnetic cations, with a shortest through-bond distance of 15.1 Å, these materials might be expected to be good examples of paramagnets. In this communication we investigate the magnetic properties of a metal thiocyanate framework Cr[Bi(SCN)6]·xH2O. We find that Cr[Bi(SCN)6]·xH2O undergoes long-range magnetic order at TN = 4.0(2) K. We use neutron powder diffraction to determine that Cr[Bi(SCN)6]·xH2O has a MnO-type {111}cubic-ordering as its ground state, consistent with frustrated nearest- and next-nearest-neighbour antiferromagnetic interactions. This suggests that appropriate design of metal thiocyanate perovskite-analogue structures may reveal a rich vein of frustrated magnetism

Definición de medidas de protección en el ámbito de las unidades mecanizadas para la minimización del riesgo de accidentes durante la fase de preparación para misiones internacionales.

Durante la realización de este trabajo se buscará la realización de un estudio y análisis de los procesos y actividades encuadradas en la fase de preparación previa a la misión. Diferenciando entre los procesos de mantenimiento realizados en el acuartelamiento, los procesos de proyección estratégica del material y personal a zona de operaciones, y los procesos de preparación del personal en territorio nacional.<br /

Non-collinear magnetism in the post-perovskite thiocyanate frameworks CsM(NCS)3

AMX 3 compounds are structurally diverse, a notable example being the post-perovskite structure which adopts a two-dimensional framework with corner-and edge-sharing octahedra. Few molecular post-perovskites are known and of these, none have reported magnetic structures. Here we report the synthesis, structure and magnetic properties of molecular post-perovskites: CsNi(NCS) 3 , a thiocyanate framework, and two new isostructural analogues CsCo(NCS) 3 and CsMn(NCS) 3. Magnetisation measurements show that all three compounds undergo magnetic order. CsNi(NCS) 3 (Curie temperature, T C = 8.5(1) K) and CsCo(NCS) 3 (T C = 6.7(1) K) order as weak ferromagnets. On the other hand, CsMn(NCS) 3 orders as an antiferromagnet (Néel temperature , T N = 16.8(8) K). Neutron diffraction data of CsNi(NCS) 3 and CsMn(NCS) 3 , show that both are non-collinear magnets. These results suggest molecular frameworks are fruitful ground for realising the spin textures required for the next generation of information technology

Controlling multiple orderings in metal thiocyanate molecular perovskites Ax{Ni[Bi(SCN)6]}

We report four new A-site vacancy ordered thiocyanate double double perovskites, A1–x{Ni[Bi(SCN)6](1–x)/3}, A = K+, NH4+, CH3(NH3)+ (MeNH3+) and C(NH2)3+ (Gua+), including the first examples of thiocyanate perovskites containing organic A-site cations. We show, using a combination of X-ray and neutron diffraction, that the structure of these frameworks depends on the A-site cation, and that these frameworks possess complex vacancy-ordering patterns and cooperative octahedral tilts distinctly different from atomic perovskites. Density functional theory calculations uncover the energetic origin of these complex orders and allow us to propose a simple rule to predict favoured A-site cation orderings for a given tilt sequence. We use these insights, in combination with symmetry mode analyses, to show that these complex orders offer a new route to non-centrosymmetric perovskites which render them as excellent candidates for piezo- and ferroelectric applications

Atypical Magnetic Behavior in the Incommensurate (CH3NH3)[Ni(HCOO)3] Hybrid Perovskite

A plethora of temperature-induced phase transitions have been observed in (CH3NH3)[M(HCOO)3] compounds, where M is Co(II) or Ni(II). Among them, the nickel compound exhibits a combination of magnetic and nuclear incommensurability below Néel temperature. Despite the fact that the zero-field behavior has been previously addressed, here we study in depth the macroscopic magnetic behavior of this compound to unveil the origin of the atypical magnetic response found in it and in its parent family of formate perovskites. In particular, they show a puzzling magnetization reversal in the curves measured starting from low temperatures, after cooling under zero field. The first atypical phenomenon is the impossibility of reaching zero magnetization, even by nullifying the applied external field and even compensating it for the influence of the Earth’s magnetic field. Relatively large magnetic fields are needed to switch the magnetization from negative to positive values or vice versa, which is compatible with a soft ferromagnetic system. The atypical path found in its first magnetization curve and hysteresis loop at low temperatures is the most noticeable feature. The magnetization curve switches from more than 1200 Oe from the first magnetization loop to the subsequent magnetization loops. A feature that cannot be explained using a model based on unbalanced pair of domains. As a result, we decipher this behavior in light of the incommensurate structure of this material. We propose, in particular, that the applied magnetic field induces a magnetic phase transition from a magnetically incommensurate structure to a magnetically modulated collinear structureThe authors thank financial support from the Ministerio de Economía y Competitividad MINECO and EU-FEDER (projects MAT2017-86453-R and PDC 2021-121076-I00). The authors are grateful to Dra. Ana Arauzo at Servicio de Medidas Físicas of the Universidad de Zaragoza for heat capacity data. O.F. acknowledges the Spanish Ministry of Universities (UNI/551/2021) and the European Union through the Funds Next GenerationS

Tailoring the physical properties of hybrid magnetic quinuclidine-based plastic compounds via weak interactions

Herein we explore the opportunities arising from combining bicyclic amine cations with halometallate anions to build organic–inorganic hybrid materials. We will use the crystal engineering approach in these materials, focusing on the tuning of the organic cation, which is mainly responsible for obtaining both new plastic states at high temperature and electrical behaviour below the plastic temperature. Precisely, this work explores the influence of the ketonization of the bicyclic quinuclidine molecule (C7H13N)+, which, combined with the tetrachloroferrate(1-) anion, gives the compound (3-oxoquinuclidinium)[FeCl4]. Interestingly, crystallization in the presence of humidity is enough to obtain an isostructural hydrate phase of formula (3-oxoquinuclidinium)[FeCl4]·H2O. Although the organic–inorganic layered structure is the same in both compounds, the three-dimensional magnetic ordering disappears after the intercalation of crystallization water molecules. A heat treatment above 400 K allows the removal of water obtaining the non-hydrate phase. Finally, the temperature evolution of the electric and magnetic behaviour will be compared with other previously reported hybrid organic–inorganic materials built with tetrachloroferrate ions and quinuclidinium-based cations.Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P, MAT2017-83631-C3-3-R and MAT2017-86453-R) is acknowledged. The authors gratefully acknowledge technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). The paper is (partly) based on the results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona and Institute Laue-Langevin (ILL) in Grenoble (Proposals 5-31-2673 and 5-12-358)

Effects of Al substitution on the multiferroic properties of TbMnO3

The effect of a small substitution of Mn with Al in TbMnO 3 has been studied. We report results of heat capacity, magnetization, and dielectric constant studies in TbMn 1-xAl xO 3 compounds (x ≤ 0.1). Al has the same valence as substituted Mn but is nonmagnetic and its small size gives rise to microstructural strain which affects the multiferroic properties of the parent compound. Long-range antiferromagnetic ordering is observed in all compounds but the transition temperature decreases as the Al content increases. TbMn 0.95Al 0.05O 3 exhibits a ferroelectric phase transition which is absent in TbMn 0.9Al 0.1O 3. The dielectric constant of the latter compound reveals a relaxor behavior suggesting the presence of nanosize polar domains for this compound. A neutron diffraction study on a single crystal of TbMn 0.9Al 0.1O 3 reveals that Mn shows a sinusoidal incommensurate ordering down to low temperature. Tb moments exhibit an incommensurate short-range ordering but the application of a magnetic field leads to metamagnetic transitions. In particular, a field parallel to the b axis induces a commensurate long-range ordering of Tb of type C xF y. The magnetic field also affects the magnetic structure of Mn3 + moments at low temperature which develop an incommensurate cycloid ordering in the ab plane. This result suggests that dilution of a magnetic multiferroic with a small nonmagnetic atom might yield materials with a relaxor to ferroelectric transition driven by a magnetic field.Financial support from Spanish MICINN (Projects No. FIS08-03951 and No. MAT2007-61621) and DGA (CAMRADS) is acknowledged. V.C. thanks the FPU research grant from MICINN.Peer Reviewe

((R)-( )-3-Hydroxyquinuclidium)[FeCl4]; a plastic hybrid compound with chirality, ferroelectricity and long range magnetic ordering

Quinuclidinium salts and their derivatives are now in the focus of materials science as building units of multifunctional materials. Their properties can be easily switchable, allowing their use in a wide range of physical applications. One type of these kinds of materials, the homochiral hybrid halometallate ferroelectric compounds, is not well understood. In this work, (R)-( )-3-quinuclidinol hydrochloride was used in the synthesis of ((R)-( )-3-hydroxyquinuclidium)[FeCl4]. The use of this enantiomeric cation forces crystallographic non-centrosymmetry, which was confirmed by polarimetry and circular dichroism spectroscopy. We studied the physical properties of this compound at different temperatures by single crystal, synchrotron and neutron powder X-ray diffraction, which showed a rich series of structural and magnetic phase transitions. From synchrotron powder X-ray diffraction data, a plastic phase was observed above 370 K (phase I). Between 370 K and ca. 310 K, an intermediate polar phase was detected, solved in a non-centrosymmetric polar space group (C2) (phase II). Below ca. 310 K, the compound crystallizes in the triclinic P1 non-centrosymmetric space group (phase III) which is maintained down to 4 K, followed by phase IV, which shows tridimensional magnetic ordering. The temperature evolution of the neutron diffraction data shows the appearance of new reflections below 4 K. These reflections can be indexed to a commensurate propagation vector k = (0, 0, 12). The magnetic structure below TN was solved in the Ps1 Shubnikov space group, which gives rise to an antiferromagnetic structure, compatible with the magnetometry measurements. Near room temperature, the crystal phase transition is associated with a dielectric change. In particular, the phase transition between phase III (S.G.:P1) and phase II (S.G.:C2) involves an increase of symmetry between two non-centrosymmetric space groups. Therefore, it allows, by symmetry, the emergence of ferroelectric and ferroelastic ordering. Piezoresponse force microscopy (PFM) imaging measurements provided evidence for polarization switching and a local ferroelectric behavior of phase III at room temperature. Additionally, the obtained butterfly curve and hysteresis loop by PFM exhibits a low coercive voltage of B10 V. This value is remarkable, since it approaches those obtained for materials with application in ferroelectric random access memories (FeRAMs).Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P, MAT2017-83631-C3-3-R, MAT2017-86453-R, PGC2018-097520-A-100 and PID2019-104050RAI00) is acknowledged. The authors gratefully acknowledge the technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). Carmen Martín is grateful to VI PPIT-2018 from Universidad de Sevilla. The paper is (partly) based on the results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona (proposal 2019083666) and Institute Laue-Langevin (ILL) of Grenoble (Proposals 5-31-2580 and 5-31-2460)

A heteropentanuclear oxalato-bridged [ReIV 4GdIII] complex: synthesis, crystal structure and magnetic properties

The compound (NBu 4) 5[Gd III{Re IVBr 4(μ-ox)} 4(H 2O)]·H 2O (1), with intramolecular antiferromagnetic coupling, is the first Re(iv) system incorporating a 4f ion. © 2012 The Royal Society of Chemistry.Financial support from the Spanish Ministerio de Ciencia e Innovación and the Generalitat Valenciana through the projects CTQ2010-15364 and PROMETEO/2009/108, respectively, is gratefully acknowledged.Peer Reviewe