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Magnetochemistry
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Magnetism of Molecular Conductors
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Magnetism of Molecular Conductors

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: closed (30 April 2017) | Viewed by 61833

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Manuel Almeida

E-Mail Website
Guest Editor
C2TN—Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, P-2695-066 Bobadela LRS, Portugal
Interests: electrical and magnetic properties of materials; multifunctional and nanostructured materials; molecular conductors; molecule based magnets; low dimensional conductors; crystal engineering

Special Issue Information

Dear Colleagues,

The study of the magnetic properties of molecular conductors has experienced, during the last few decades, a very significant evolution comprising systems of increasing molecular complexity, and moving towards multifunctional materials. In this context, molecular magnetic conductors recently emerged at the intersection between the fields of molecule-based conductors and molecule-based magnets, as a very exciting class of multifunctional materials, where the interplay between charge, structure, and magnetism in general, and particularly the interaction and synergy between conduction electrons and localized magnetic moments, can lead to new phenomena, complex phase diagrams and ground states, with a large potential of technological applications namely in electronic devices and in spintronics. Among these phenomena are unusual field induced transitions including magnetic field induced superconductivity, very large magnetorresistence effects, switchable conductors by magnetic field, changes of magnetic ordering, spin state, etc.

This Special Issue of Magnetochemistry aims at publishing a collection of research contributions illustrating the recent achievements in all aspects of the development, study and understanding of the magnetic properties of molecular conductors and their applications, namely in the topics listed below.

Prof. Dr. Manuel Almeida
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Magnetochemistry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • The molecular approaches to the preparation of Multifunctional electrical and magnetic materials
  • π-d interactions in molecular conductors
  • Magnetic conductors
  • Magnetic Superconductors
  • Field induced superconductivity
  • Spin Crossover conductors
  • Photomagnetic response in molecular conductors
  • Photo switchable spin-crossover molecular conductor
  • Magnetic field induced transitions.
  • Magnetic response of strongly correlated electronic systems

Published Papers (13 papers)

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Editorial

Jump to: Research, Review

167 KiB  
Editorial
Magnetism of Molecular Conductors
by Manuel Almeida
Magnetochemistry 2017, 3(3), 23; https://doi.org/10.3390/magnetochemistry3030023 - 27 Jun 2017
Cited by 1 | Viewed by 2637
Abstract
The study of the magnetic properties of molecular conductors has experienced, during the last decades, a very significant evolution, comprising systems of increasing molecular complexity and moving towards multifunctional materials, namely by their incorporation in conducting networks of different paramagnetic centers.[...] Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)

Research

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3158 KiB  
Article
The Solid Solutions (Per)2[PtxAu(1−x)(mnt)2]; Alloying Para- and Diamagnetic Anions in Two-Chain Compounds
by Manuel Matos, Gregoire Bonfait, Isabel C. Santos, Mónica L. Afonso, Rui T. Henriques and Manuel Almeida
Magnetochemistry 2017, 3(2), 22; https://doi.org/10.3390/magnetochemistry3020022 - 13 Jun 2017
Cited by 5 | Viewed by 4106
Abstract
The α-(Per)2[M(mnt)2] compounds with M = Pt and Au are isostructural two-chain solids that in addition to partially oxidized conducting perylene chains also contain anionic chains that can be either paramagnetic in the case of M = Pt or [...] Read more.
The α-(Per)2[M(mnt)2] compounds with M = Pt and Au are isostructural two-chain solids that in addition to partially oxidized conducting perylene chains also contain anionic chains that can be either paramagnetic in the case of M = Pt or diamagnetic for M = Au. The electrical transport and magnetic properties of the solid solutions (Per)2[Ptx-Au(1−x)(mnt)2] were investigated. The incorporation of paramagnetic [Pt(mnt)2] impurities in the diamagnetic chains, and the effect of breaking the paramagnetic chains with diamagnetic centers for the low and high Pt range of concentrations were respectively probed. In the low Pt concentration range, there is a fast decrease of the metal-to-insulator transition from 12.4 K in the pure Au compound to 9.7 K for x = 0.1 comparable to the 8.1 K in the pure Pt compound. In the range x = 0.50−0.95, only β-phase crystals could be obtained. The spin-Peierls transition of the pure Pt compound, simultaneous with metal-to-insulator (Peierls) transition is still present for 2% of diamagnetic impurities (x = 0.98) with transition temperature barely affected. Single crystal X-ray diffraction data obtained a high-quality structural refinement of the α-phase of the Au and Pt compounds. The β-phase structure was found to be composed of ordered layers with segregated donors and anion stacks, which alternate with disordered layers. The semiconducting properties of the β-phase are due to the disorder localization effects. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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2214 KiB  
Article
Dye-Sensitized Molecular Charge Transfer Complexes: Magnetic and Conduction Properties in the Photoexcited States of Ni(dmit)2 Salts Containing Photosensitive Dyes
by Ryoma Yamamoto, Takashi Yamamoto, Keishi Ohara and Toshio Naito
Magnetochemistry 2017, 3(2), 20; https://doi.org/10.3390/magnetochemistry3020020 - 19 May 2017
Cited by 8 | Viewed by 4383
Abstract
Photosensitive dyes often induce charge transfer (CT) between adjacent chemical species and themselves under irradiation of appropriate wavelengths. Because of the reversibility and selectivity of such CT, it is considered to be interesting to utilize such dyes as optically controllable trigger components for [...] Read more.
Photosensitive dyes often induce charge transfer (CT) between adjacent chemical species and themselves under irradiation of appropriate wavelengths. Because of the reversibility and selectivity of such CT, it is considered to be interesting to utilize such dyes as optically controllable trigger components for conduction and magnetism in the photoexcited states of organic materials. Based on this idea, such a type of new salts, i.e., γ- and δ-DiCC[Ni(dmit)2] in addition to DiCC2[Ni(dmit)2]3 have been prepared, characterized and their physical and structural properties have been examined both under dark and irradiated conditions (dmit2− = 1,3-dithiole-2-thione-4,5-dithiolate, DiCC+ = 3,3′-Dihexyloxacarbocyanine monocation). Among them, under UV (254–450 nm) irradiation, δ-DiCC[Ni(dmit)2] exhibited photoconductivity being six times as high as its dark conductivity at room temperature. The electron spin resonance (ESR) spectra have demonstrated that there are photoexcited spins on both DiCC and [Ni(dmit)2] species as a result of the CT transition between them, serving as localized spins (DiCC) and carriers ([Ni(dmit)2]), respectively. The results obtained in this work have indicated that the strategy mentioned above is effective in developing organic photoresponsive semiconductors with paramagnetism. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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2787 KiB  
Article
Charge Ordering Transitions of the New Organic Conductors δm- and δo-(BEDT-TTF)2TaF6
by Tadashi Kawamoto, Kohei Kurata, Takehiko Mori and Reiji Kumai
Magnetochemistry 2017, 3(1), 14; https://doi.org/10.3390/magnetochemistry3010014 - 01 Mar 2017
Cited by 7 | Viewed by 3720
Abstract
Structural, transport, and magnetic properties of new organic conductors composed of (BEDT-TTF) 2 TaF 6 , where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, have been investigated. Two δ -type polymorphs, monoclinic and orthorhombic phases are obtained by the electrocrystallization. Both phases show a semiconductor-insulator phase transition [...] Read more.
Structural, transport, and magnetic properties of new organic conductors composed of (BEDT-TTF) 2 TaF 6 , where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, have been investigated. Two δ -type polymorphs, monoclinic and orthorhombic phases are obtained by the electrocrystallization. Both phases show a semiconductor-insulator phase transition at 276 K and 300 K for the monoclinic and orthorhombic phases, respectively; the ground state of both salts is a nonmagnetic insulating state. The low-temperature X-ray diffraction measurements show two-fold superlattice reflections in the intercolumnar direction. The low-temperature crystal structures show a clear charge ordered state, which is demonstrated by the molecular shape and intramolecular bond lengths. The observed checkerboard charge ordered state is in agreement with the charge ordering in a dimer Mott insulator. If we distinguish between the monoclinic and orthorhombic phases, the transition temperature of the δ -type (BEDT-TTF) 2 M F 6 conductors ( M = P, As, Sb, and Ta) increases continuously with increasing the anion volume. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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4973 KiB  
Article
New Dmit-Based Organic Magnetic Conductors (PO-CONH-C2H4N(CH3)3)[M(dmit)2]2 (M = Ni, Pd) Including an Organic Cation Derived from a 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl (PO) Radical
by Hiroki Akutsu, Scott S. Turner and Yasuhiro Nakazawa
Magnetochemistry 2017, 3(1), 11; https://doi.org/10.3390/magnetochemistry3010011 - 25 Feb 2017
Cited by 6 | Viewed by 4736
Abstract
We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C2H4N(CH3)3)[Ni(dmit)2]2·CH3CN and (PO-CONH-C2H4N(CH3)3)[Pd(dmit)2]2 where PO [...] Read more.
We have prepared two dmit-based salts with a stable organic radical-substituted ammonium cation, (PO-CONH-C2H4N(CH3)3)[Ni(dmit)2]2·CH3CN and (PO-CONH-C2H4N(CH3)3)[Pd(dmit)2]2 where PO is 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl and dmit is 2-Thioxo-1,3-dithiol-4,5-dithiolate. The salts are not isostructural but have similar structural features in the anion and cation packing arrangements. The acceptor layers of both salts consist of tetramers, which gather to form 2D conducting layers. Magnetic susceptibility measurements indicate that the Ni salt is a Mott insulator and the Pd salt is a band insulator, which has been confirmed by band structure calculations. The cationic layers of both salts have a previously unreported polar structure, in which the cation dipoles order as ➚➘➚➘ along the acceptors stacking direction to provide dipole moments. The dipole moments of nearest neighbor cation layers are inverted in both salts, indicating no net dipole moments for the whole crystals. The magnetic network of the [Ni(dmit)2] layer of the Ni salt is two-dimensional so that the magnetic susceptibility would be expected to obey the 1D or 2D Heisenberg model that has a broad maximum around T ≈ θ. However, the magnetic susceptibility after subtraction of the contribution from the PO radical has no broad maximum. Instead, it shows Curie–Weiss behavior with C = 0.378 emu·K/mol and θ = −35.8 K. The magnetic susceptibility of the Pd salt obeys a Curie–Weiss model with C = 0.329 emu·K·mol−1 and θ = −0.88 K. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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8678 KiB  
Article
The Highly Conducting Spin-Crossover Compound Combining Fe(III) Cation Complex with TCNQ in a Fractional Reduction State. Synthesis, Structure, Electric and Magnetic Properties
by Yuri N. Shvachko, Denis V. Starichenko, Aleksander V. Korolyov, Alexander I. Kotov, Lev I. Buravov, Vladimir N. Zverev, Sergey V. Simonov, Leokadiya V. Zorina and Eduard B. Yagubskii
Magnetochemistry 2017, 3(1), 9; https://doi.org/10.3390/magnetochemistry3010009 - 22 Feb 2017
Cited by 14 | Viewed by 5465
Abstract
Three systems [Fe(III)(sal2-trien)](TCNQ)n·X (n = 1, 2, X = MeOH, CH3CN, H2O) showing spin-crossover transition, conductivity and ferromagnetic coupling were synthesized and studied by X-ray diffraction, Montgomery method for resistivity, SQUID magnetometry and [...] Read more.
Three systems [Fe(III)(sal2-trien)](TCNQ)n·X (n = 1, 2, X = MeOH, CH3CN, H2O) showing spin-crossover transition, conductivity and ferromagnetic coupling were synthesized and studied by X-ray diffraction, Montgomery method for resistivity, SQUID magnetometry and X-band EPR. Spin-spin interactions between local magnetic moments of Fe(III) ions and electron spins of organic TCNQ network were discovered and discussed within the framework of intermolecular superexchange coupling. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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3916 KiB  
Article
New Ethylenedithio-TTF Containing a 2,2,5,5-Tetramethylpyrrolin-1-yloxyl Radical through a Vinylene Spacer and Its FeCl4− Salt—Synthesis, Physical Properties and Crystal Structure Analyses
by Kazuki Horikiri and Hideki Fujiwara
Magnetochemistry 2017, 3(1), 8; https://doi.org/10.3390/magnetochemistry3010008 - 09 Feb 2017
Cited by 3 | Viewed by 3471
Abstract
To develop novel magnetic conductors exhibiting conducting/magnetic bifunctionalities and peculiar responses to applied magnetic fields, we synthesized new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a 2,2,5,5-tetramethylpyrrolin-1-yloxyl radical through a π-conjugated vinylene spacer 1 and examined its electronic and crystal structures, and physical properties. We also [...] Read more.
To develop novel magnetic conductors exhibiting conducting/magnetic bifunctionalities and peculiar responses to applied magnetic fields, we synthesized new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a 2,2,5,5-tetramethylpyrrolin-1-yloxyl radical through a π-conjugated vinylene spacer 1 and examined its electronic and crystal structures, and physical properties. We also prepared its cation radical salts by an electrochemical oxidation method and successfully cleared the crystal structures and magnetic properties of the cation radical salts, 1·FeCl4 and 1·GaCl4. These salts have strongly dimerized one-dimensional arrays of the fully oxidized donor molecules, giving rise to the formation of spin-singlet state of the π cation radical spins in the dimer. On the other hand, the FeCl4- anion locates on the side of the dimers with very short S-Cl contacts and mediates very strong π-d interaction between the donor and anion moieties, resulting in the antiferromagnetic behavior of the Weiss temperature of θ = -3.9 K through its d-π-d interaction. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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4577 KiB  
Article
Mn‐Containing Paramagnetic Conductors with Bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF)
by Samia Benmansour, Yolanda Sánchez‐Máez and Carlos J. Gómez‐García
Magnetochemistry 2017, 3(1), 7; https://doi.org/10.3390/magnetochemistry3010007 - 09 Feb 2017
Cited by 11 | Viewed by 4038
Abstract
Two novel paramagnetic conductors have been prepared with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF = ET) and paramagnetic Mn‐containing metallic complexes: κ′‐ET4[KMnIII(C2O4)3]∙PhCN (1) and ET[MnIICl4]∙H2O (2). Compound 1 represents the first Mn‐containing ET salt of the large Day’s series of oxalato‐based molecular conductors and [...] Read more.
Two novel paramagnetic conductors have been prepared with the organic donor bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF = ET) and paramagnetic Mn‐containing metallic complexes: κ′‐ET4[KMnIII(C2O4)3]∙PhCN (1) and ET[MnIICl4]∙H2O (2). Compound 1 represents the first Mn‐containing ET salt of the large Day’s series of oxalato‐based molecular conductors and superconductors formulated as (ET)4[AM(C2O4)3]∙G (A+ = H3O+, NH4+, K+, ...; MIII = Fe, Cr, Al, Co, ...; G = PhCN, PhNO2, PhF, PhCl, PhBr, ...). It crystallizes in the orthorhombic pseudo‐κ phase where dimers of ET molecules are surrounded by six isolated ET molecules in the cationic layers. The anionic layers contain the well‐known hexagonal honey‐comb lattice with Mn(III) and H3O+ ions connected by C2O42- anions. Compound 2 is one of the very few examples of ET salts containing ET2+. It also presents alternating cationic‐anionic layers although the ET molecules lie parallel to the layers instead of the typical almost perpendicular orientation. Both salts are semiconductors with room temperature conductivities of ca. 2 x 10-5 and 8 x 10−5 S/cm and activation energies of 180 and 210 meV, respectively. The magnetic properties are dominated by the paramagnetic contributions of the high spin Mn(III) (S = 2) and Mn(II) (S = 5/2) ions. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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Graphical abstract

2891 KiB  
Article
Synthesis and Characterization of Ethylenedithio-MPTTF-PTM Radical Dyad as a Potential Neutral Radical Conductor
by Manuel Souto, Dan Bendixen, Morten Jensen, Valentín Díez-Cabanes, Jérôme Cornil, Jan O. Jeppesen, Imma Ratera, Concepció Rovira and Jaume Veciana
Magnetochemistry 2016, 2(4), 46; https://doi.org/10.3390/magnetochemistry2040046 - 16 Dec 2016
Cited by 4 | Viewed by 5414
Abstract
During the last years there has been a high interest in the development of new purely-organic single-component conductors. Very recently, we have reported a new neutral radical conductor based on the perchlorotriphenylmethyl (PTM) radical moiety linked to a monopyrrolo-tetrathiafulvalene (MPTTF) unit by a [...] Read more.
During the last years there has been a high interest in the development of new purely-organic single-component conductors. Very recently, we have reported a new neutral radical conductor based on the perchlorotriphenylmethyl (PTM) radical moiety linked to a monopyrrolo-tetrathiafulvalene (MPTTF) unit by a π-conjugated bridge (1) that behaves as a semiconductor under high pressure. With the aim of developing a new material with improved conducting properties, we have designed and synthesized the radical dyad 2 which was functionalized with an ethylenedithio (EDT) group in order to improve the intermolecular interactions of the tetrathiafulvalene (TTF) subunits. The physical properties of the new radical dyad 2 were studied in detail in solution to further analyze its electronic structure. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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Review

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1961 KiB  
Review
Axially Ligated Phthalocyanine Conductors with Magnetic Moments
by Tamotsu Inabe and Noriaki Hanasaki
Magnetochemistry 2017, 3(2), 18; https://doi.org/10.3390/magnetochemistry3020018 - 23 Apr 2017
Cited by 5 | Viewed by 4733
Abstract
This mini-review describes electrical conductivity, magnetic properties, and magnetotransport properties of one-dimensional partially oxidized salts composed of axially ligated phthalocyanines, TPP[M(Pc)(CN)2]2 (TPP = tetraphenylphosphonium, Pc = phthalocyaninato), with M of Fe (d5, S = 1/2) and Cr (d [...] Read more.
This mini-review describes electrical conductivity, magnetic properties, and magnetotransport properties of one-dimensional partially oxidized salts composed of axially ligated phthalocyanines, TPP[M(Pc)(CN)2]2 (TPP = tetraphenylphosphonium, Pc = phthalocyaninato), with M of Fe (d5, S = 1/2) and Cr (d3, S = 3/2). These salts are isomorphous, and π–π interactions in the crystal, that becomes the origin of the charge carriers, are nearly the same. Both the Fe and Cr salts show carrier localization and charge disproportionation which is enhanced by the interaction between local magnetic moments and conduction π-electrons (π–d interaction). However, the magnetic properties are slightly different between them. M = Fe has been found to show unique anisotropic magnetic properties and antiferromagnetic short-range magnetic order between the d-spins. On the other hand, for M = Cr, its magnetic moment is isotropic. Temperature dependence of the magnetic susceptibility shows typical Curie–Weiss behavior with negative Weiss temperature, but the exchange interaction is complicated. Both M = Fe and M = Cr show large negative magnetoresistance, reflecting the difference in the anisotropy. The magnetoresistance ratio (MR) is larger in the Fe system than in the Cr system in the low magnetic field range, but MR in the Cr system exceeds that in the Fe system when the magnetic field becomes higher than 15 T. We discuss the mechanism of the giant negative magnetoresistance with reference to the d–d, π–d, and π–π interactions. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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25015 KiB  
Review
Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties
by Maria Laura Mercuri, Francesco Congiu, Giorgio Concas and Suchithra Ashoka Sahadevan
Magnetochemistry 2017, 3(2), 17; https://doi.org/10.3390/magnetochemistry3020017 - 19 Apr 2017
Cited by 71 | Viewed by 8748
Abstract
The aim of the present work is to highlight the unique role of anilato-ligands, derivatives of the 2,5-dioxy-1,4-benzoquinone framework containing various substituents at the 3 and 6 positions (X = H, Cl, Br, I, CN, etc.), in engineering a great variety of new [...] Read more.
The aim of the present work is to highlight the unique role of anilato-ligands, derivatives of the 2,5-dioxy-1,4-benzoquinone framework containing various substituents at the 3 and 6 positions (X = H, Cl, Br, I, CN, etc.), in engineering a great variety of new materials showing peculiar magnetic and/or conducting properties. Homoleptic anilato-based molecular building blocks and related materials will be discussed. Selected examples of such materials, spanning from graphene-related layered magnetic materials to intercalated supramolecular arrays, ferromagnetic 3D monometallic lanthanoid assemblies, multifunctional materials with coexistence of magnetic/conducting properties and/or chirality and multifunctional metal-organic frameworks (MOFs) will be discussed herein. The influence of (i) the electronic nature of the X substituents and (ii) intermolecular interactions i.e., H-Bonding, Halogen-Bonding, π-π stacking and dipolar interactions, on the physical properties of the resulting material will be also highlighted. A combined structural/physical properties analysis will be reported to provide an effective tool for designing novel anilate-based supramolecular architectures showing improved and/or novel physical properties. The role of the molecular approach in this context is pointed out as well, since it enables the chemical design of the molecular building blocks being suitable for self-assembly to form supramolecular structures with the desired interactions and physical properties. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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4717 KiB  
Review
Peierls and Spin-Peierls Instabilities in the Per2[M(mnt)2] Series of One-Dimensional Organic Conductors; Experimental Realization of a 1D Kondo Lattice for M = Pd, Ni and Pt
by Jean-Paul Pouget, Pascale Foury-Leylekian and Manuel Almeida
Magnetochemistry 2017, 3(1), 13; https://doi.org/10.3390/magnetochemistry3010013 - 25 Feb 2017
Cited by 12 | Viewed by 5065
Abstract
We consider structural instabilities exhibited by the one-dimensional (1D) (arene)2X family of organic conductors in relation with their electronic and magnetic properties. With a charge transfer of one electron to each anion X, these salts exhibit a quarter-filled (hole) conduction band [...] Read more.
We consider structural instabilities exhibited by the one-dimensional (1D) (arene)2X family of organic conductors in relation with their electronic and magnetic properties. With a charge transfer of one electron to each anion X, these salts exhibit a quarter-filled (hole) conduction band located on donor stacks. Compounds built with donors such as fluorenthene, perylene derivatives and anions X such as PF6 or AsF6 exhibit a high temperature (TP ~ 170 K) conventional Peierls transition that is preceded by a sizeable regime of 1D 2kF charge density wave fluctuations (kF is the Fermi wave vector of the 1D electron gas located on Per stack). Surprisingly, and probably because of the presence of a multi-sheet warped Fermi surface, the critical temperature of the Peierls transition is considerably reduced in the perylene series α-(Per)2[M(mnt)2] where X is the dithiolate molecule with M = Au, Cu, Co and Fe. Special attention will be devoted to physical properties of α-(Per)2[M(mnt)2] salts with M = Pt, Pd and Ni which incorporate segregated S = 1/2 1D antiferromagnetic (AF) dithiolate stacks coexisting with 1D metallic Per stacks. We analyze conjointly the structural and magnetic properties of these salts in relation with the 1D spin-Peierls (SP) instability located on the dithiolate stacks. We show that the SP instability of Pd and Ni derivatives occurs in the classical (adiabatic) limit while the SP instability of the Pt derivative occurs in the quantum (anti-adiabatic) limit. Furthermore, we show that in Pd and Ni derivatives 1st neighbor direct and frustrated 2nd neighbor indirect (through a fine tuning with the mediated 2kF RKKY coupling interaction on Per stacks) AF interactions add their contribution to the SP instability to stabilize a singlet-triplet gap. Our analysis of the data show unambiguously that magnetic α-(Per)2[M(mnt)2] salts exhibit the physics expected for a two chain Kondo lattice. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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4509 KiB  
Review
Antiferromagnetic Insulating Ground State of Molecular π-d System Λ-(BETS)2FeCl4 (BETS = Bis(ethylenedithio)tetraselenafulvalene): A Theoretical and Experimental Review
by Yugo Oshima, Heng‐Bo Cui and Reizo Kato
Magnetochemistry 2017, 3(1), 10; https://doi.org/10.3390/magnetochemistry3010010 - 24 Feb 2017
Cited by 17 | Viewed by 4301
Abstract
The πd molecular conductor λ‐(BETS)2FeCl4, where BETS is bis(ethylenedithio) tetraselenafulvalene, has attracted considerable interest for the discovery of its field induced superconducting state. A mystery of this system is its antiferromagnetic insulating ground state. The point still under strong debate is whether the [...] Read more.
The πd molecular conductor λ‐(BETS)2FeCl4, where BETS is bis(ethylenedithio) tetraselenafulvalene, has attracted considerable interest for the discovery of its field induced superconducting state. A mystery of this system is its antiferromagnetic insulating ground state. The point still under strong debate is whether the d spins in Fe3+ are ordered or not. Here, we review experimental and theoretical studies on the antiferromagnetic insulating phase in λ‐(BETS)2FeCl4 and mention our perspective based on our ESR measurements for λ‐(BETS)2FexGa1−xCl4. Our ESR results indicate that the π‐d interaction in the system is very strong and there is no sign of paramagnetic Fe spins in the antiferromagnetic ground state. Full article
(This article belongs to the Special Issue Magnetism of Molecular Conductors)
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