Incommensurate crystal structure, thermal expansion study and magnetic properties of (dimethylimidazolium)2[Fe2Cl6(?-O)]

A thorough characterization of the title compound, (dimim)2[Fe2Cl6(µ-O)], consisting of a (µ-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group PĪ(/α/β/γ)0 with modulation vector q=0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (µ-oxido)-bridged binuclear iron(III) complex, as well as the molecular motion of the imidazolium cation within the crystalline structure as a response to the temperature effect. Finally, we present a deep magnetic study based on magnetic susceptibility, magnetization and Mössbauer measurements, where the strong antiferromagnetic exchange coupling detected is due to the occurrence of a µ-oxido bridge between the Fe(III), giving rise to an intra-dimeric antiferromagnetic exchange coupling of -308 cm-1.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)

Atypical magnetic behavior in the incommensurate [CH3NH3][Ni(HCOO)3][CH_3NH_3][Ni(HCOO)_3] hybrid perovskite

A plethora of temperature induced phase transitions have been observed in $[CH_3NH_3][M(HCOO)_3]$ compounds, where M is Co(II) or Ni(II). Among them, the nickel compound exhibits a combination of magnetic and nuclear incommensurabil-ity below N\'eel 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 phenomena is the im-possibility of reaching zero magnetization, even by nullifying the applied external field and even compensating it for the influence 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 mag-netic phase transition from a magnetically incommensurate structure to a magnetically commensurate structure.Comment: 9 pages, 7 figures, 1 tabl

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

((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)

Mode-crystallography analysis and magnetic structures of SrLnFeRuO6 (Ln = La, Pr, Nd) disordered perovskites

The crystal and magnetic structures of SrLnFeRuO6 (Ln = La, Pr, Nd) double perovskites have been investigated. All compounds crystallize with an orthorhombic Pbnm structure at room temperature. These materials show complete chemical disorder of Fe and Ru cations for all compounds. The distortion of the structure, relative to the ideal cubic perovskite, has been decomposed into distortion modes. It has been found that the primary modes of the distortion are octahedral tilting modes: R + 4 and M + 3. The crystal structure of SrPrFeRuO6 has been studied from room temperature up to 1200 K by neutron powder diffraction. There is a structural phase transition from orthorhombic (space group Pbnm) to trigonal (space group ) at T = 1075 K. According to group theory no second-order transition is possible between these symmetries. Magnetic ordering for all the compounds is described by the magnetic propagation vector (0,0,0). SrPrFeRuO6 shows ferrimagnetic order below ca 475 K, while SrLaFeRuO6 (below ca 450 K) and SrNdFeRuO6 (below ca 430 K) exhibit canted-antiferromagnetic order. The magnetic moments at low temperatures are m(Fe/Ru) = 1.88 (3)B for SrLaFeRuO6 (2 K), m(Pr) = 0.46 (4)B and m(Fe/Ru) = 2.24B for SrPrFeRuO6 (2 K), and m(Fe/Ru) = 1.92B for SrNdFeRuO6 (10 K). © 2012 International Union of Crystallography.This work has been supported by ILL (grant MBR-GL/09-056 and MBR-GL/11-050), the Spanish Ministry of Science and Innovation (project MAT2008-05839) and the European Commission under the 7th Framework Program through the ‘Research Infrastructures’ action of the ‘Capacities’ Program, Contract No: CP-CSA_INFRA-2008-1.1.1 Number 226507- NMI3. The authors are grateful to FRMII (exp. 4456), ILL (exp. 5-24-458) and PSI (exp. 20101302) for the beamtime allocation and the instrument local contacts Dr Markus Hoelzel (SPODI, FRMII), Dr Gabriel Cuello (D2B, ILL) and Dr Vladimir Pumjakushin (HRPT, SINQ, PSI) for their kind help and technical assistance.Peer Reviewe

Slow magnetic relaxation in carbonato-bridged dinuclear lanthanide(iii) complexes with 2,3-quinoxalinediolate ligands

The coordination chemistry of the 2,3-quinoxalinediolate ligand with different lanthanide(iii) ions in basic media in air affords a new family of carbonato-bridged M 2 III compounds (M = Pr, Gd and Dy), the Dy 2 III analogue exhibiting slow magnetic relaxation behaviour typical of single-molecule magnets. This journal is © 2012 The Royal Society of Chemistry.This work was supported by the MICINN (Spain) (Projects CTQ2010-15364 and CSD2007-00010), the Generalitat Valenciana (Spain) (Projects PROMETEO/2009/108 and ISIC/2012/002) and the ESRF (France) (Projects HS3902 and 25-01-783).Peer Reviewe

The new D1B of the Institute Laue Langevin

Resumen del trabajo presentado a la VI Reunión de la Sociedad Española de Técnicas Neutrónicas celebrada en Segovia (España) del 24 al 27 de junio de 2012.-- et al.D1B is a high flux medium resolution powder diffractometer instrument located in the hall-guide of the Institute Laue Langevin (Grenoble, France). Its singular geometrical characteristics together with the two monochromators avaible make this instrument suitable for studying a large type of polycrystalline materiales. Since 1998 D1B is a CRG (collaborating researching group) instrument, which works under the supervision of CSIC and CNRS (Centre National de la Récherche Scientifique). The available beam time is sharing between ILL (50%), CNRS (27.5%) and CSIC(22.5%). The staff od D1B either from the CNRS or CSIC supports technically and scientifically the experiments of both ILL and CRG beam time. In 2008, the Spanish CRG of D1B obtained funding for building a new detector for the instrument and a radial oscillating collimator (ROC). The old detector of D1B had been running for nearly forty years and the risk of breaking down were high. After years of hard work, finally in 2011 the new detector and ROC have been commissioned and they are now at the disposal of the users of D1B. The technical characteristics of the new detector and ROC will be presented, as well as a short review of the different types of experiments.Authors acknowledge Ministerio de Economía y Competitividad for funding the refurbishment od D1B. MCINN-ICTS-2008-36 titulado "Detector de neutrones térmicos basado en tecnologías MWGC"; ICTS-06-11 titulado "Cosntrucción de un nuevo detector de neutrones basado en tecnología MSGC para el instrumento CRG-D1B".Peer reviewe

Spin localization in [Mn3(suc)2(ina)2]n: An homometallic molecular 3D ferrimagnet

Trabajo presentado al "International Workshop on Single-Crystal Diffraction with Polarised Neutrons" celebrado en el Institut Laue-Langevin de Grenoble (Francia) del 23 al 25 de enero de 2013.This work has been partially funded through projects: MAT2011-27233-C02-02 and CSD2007-00010 from the spanish MICINN.Peer Reviewe

Spin density distribution in a mixed valence iron(II)-iron(III) formate framework presenting electric and magnetic order

Trabajo presentado al "International Workshop on Single-Crystal Diffraction with Polarised Neutrons" celebrado en el Institut Laue-Langevin de Grenoble (Francia) del 23 al 25 de enero de 2013.This work has been partially funded through projects: MAT2011-27233-C02-02 and CSD2007-00010 from the Spanish Ministry of Science.Peer Reviewe

A multifunctional magnetic material under pressure

FeII(Metz)6](FeIIIBr4) 2 (Metz=1-methyltetrazole) is one of the rare systems combining spin-crossover and long-range magnetic ordering. A joint neutron and X-ray diffraction and magnetometry study allows determining its collinear antiferromagnetic structure, and shows an increase of the Néel temperature from 2.4 K at ambient pressure, to 3.9 K at 0.95 GPa. Applied pressure also enables a full high-spin to low-spin switch at ambient temperature.This work was supported by the Spanish MINECO and FEDER, projects MAT2011–24284, MAT2011–27233-C02–02 and MAT2012–38318-C03–01.Peer Reviewe