Strong Antiferromagnetic Coupling Research Articles

Probing electronic structures of redox-active ruthenium-quinonoids appended with polycyclic aromatic hydrocarbon (PAH) backbone

The newly designed electrically neutral complexes [Ru(acac)2(Q)] (1–3) involving redox-active polycyclic aromatic hydrocarbon (PAH) derived quinonoids (Q): Q1(O,O) (1) and Q2(O,NH) (2), Q2(NH,NH) (3) (acac = acetylacetonate) were prepared from the metal precursor [RuII(acac)2(CH3CN)2] and preformed pyrene-4,5-dione (Q1) and partially deprotonated pyrene-4,5-diamine (H4Q2), respectively. The structural characterization of 1–3 established their molecular identities including intermolecular π-π stacking interactions between the extended π-system of pyrene in the adjacent molecules and the hydrogen bonded 1D-polymeric form of 3. The redox sensitive C-O and C-N bond distances of Q in 1, 2 and 3 revealed the dominating ground state electronic forms of [(acac)2RuIII-Q1(O,O)•−] (S = 0), [(acac)2RuIII-Q2(O,NH)•−] (S = 0) and [(acac)2RuII-Q2(NH,NH)o] (S = 0), respectively, where strong antiferromagnetic coupling between RuIII(t2g5) and Q•− resulted in S = 0 state in 1 or 2. Complexes 1–3 exhibited reversible single oxidation and reduction within the potential window of ± 1.5 V versus SCE in CH3CN, which progressively shifted to the negative potential on moving from 1 to 2 to 3, primarily due to the difference in electronegativity between O and N donors of Q. The collective consideration of experimental (EPR, electronic spectra) and theoretical (DFT, TD-DFT) results of 1n-3n (n = +1, 0, −1) revealed (i) extensive mixing of metal–ligand orbitals due to the inherent covalency factor and (ii) Q•− and RuII based oxidations of 1/2 and 3, respectively, led to the {RuIII-Qo} electronic form at the metal–ligand interface of the oxidized state (1+-3+), while the reduced state (1 − −3 −) could best be described by the resonating form of {RuII-Q•−}↔{RuIII-Q2−}.

Linear pentanuclear nickel(II) and tetranuclear copper(II) complexes with pyrazine-modulated tripyridyldiamine ligand: Synthesis, structure and properties

By using tripyridyldiamine ligand, N,N’-di(pyrazin-2-yl)pyridine-2,6-diamine (H2dpzpda), linear pentanuclear nickel(II) [Ni5(µ5-dpzpda)4Cl2] (1) and tetranuclear copper(II) [Cu4(Hdpzpda)2(CH3COO)6] (2) complexes were first synthesized and structurally characterized. This pentanickel linear metal chain is helically wrapped by four syn-syn-syn-syn type dpzpda2- ligands. There are two types of NiNi distances existing in the complex. The terminal NiNi distances bonded to the axial ligand are longer (2.3877(8) Å) affected by the axial ligands. The inner NiNi distances are very short and remain constant (2.3071(6) Å). Two terminal Ni(II) ions bonded to the axial ligands are in a square-pyramidal (NiN4Cl) environment and exhibit long NiN bonds (2.097(4) Å), which are consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions display short NiN (1.8915(8)–1.903(4) Å) bond distances, which are consistent with a square planar (NiN4), the diamagnetic arrangement of a low-spin Ni(II) configuration. Temperature-dependent magnetic research revealed an antiferromagnetic interaction between the two terminal atoms through a superexchange pathway along metal cores with a parameter of about −51.0 cm–1. Observation of the first oxidation peak in the cyclic voltammograms of 1 at +1.206 V revealed that this complex is the most resistant to oxidation among all known pentanuclear nickel strings with unmodulated and modulated oligo-α-pyridylamido ligands. The structure of 2 consists of four copper atoms linearly placed with a copper(II) acetate dimer in the centre. In complex 2 ligand H2dpzpda coordinates to the Cu(II) atoms as a tetradentate ligand in an all anti conformation. Copper complex 2 is built to a 1-D supramolecular chain structure through intermolecular hydrogen bond and strong π-π interaction (3.19 Å) between the pyridine and pyrazine rings. From the magnetic susceptibility data, 2 shows strong antiferromagnetic coupling, which was satisfactorily fitted using Hamiltonian H = J1(S1S2 + S3S4) + J2S2S3. The best fitting result were obtained with the parameters J1 = 10.64 cm−1, J2 = −175.36 cm−1, g = 2.11.

Effect of Symmetry Breaking on Interlayer Exchange Coupling and Electrical Conduction in SrRuO3–PrMnO3 Superlattices

AbstractThe breaking of orthorhombic to tetragonal crystal symmetry is realized by increasing the PrMnO3 layer thickness in the superlattices consisting two ferromagnets, SrRuO3 and PrMnO3. The octahedral rotation pattern is a+c−c− and a0a0c− type for the superlattices with orthorhombic and tetragonal phase, respectively, inferred in the simulated projected density of states. The 15% reduction in orbital occupancy due to the a0a0c− type octahedral rotation compared to that of the a+c−c− type suggests the presence of stronger antiferromagnetic (AFM) coupling. The larger orbital overlapping leads to a stronger spin–orbit coupling, associated with a shift of 42.8% of the minor in‐plane field cooled (FC) magnetic hysteresis loop(M(H)) along the magnetization axis in orthorhombic superlattices. While, minor in‐plane FC M(H) shifts along the field axis due to the strong AFM coupling in tetragonal superlattices. In field‐dependent magnetoresistance, the rotation of spins in the antiferromagnetically coupled interfacial layers is detected as a unique anomaly, which is stronger in the superlattices for the biased spins and tetragonal symmetry than the pinned spins and orthorhombic symmetry. The results demonstrate that the tuning of interfacial exchange coupling and spin‐dependent transport by controlling structural distortion could be used as a tool in fabricating modern spintronics‐based devices.

Spin dynamics of antiferromagnetically coupled bilayers—the case of Cr2TeO6

Understanding the dynamics of interacting quantum spins has been one of the active areas of condensed matter physics research. Recently, extensive inelastic neutron scattering measurements have been carried out in an interesting class of systems, Cr2(Te, W, Mo)O6. These systems consist of bilayers of Cr3+ spins (S = 3/2) with strong antiferromagnetic inter-bilayer coupling (J) and tuneable intra-bilayer coupling (j) from ferro (for W and Mo) to antiferro (for Te). In the limit when , the system reduces to weakly interacting quantum spin-3/2 dimers. In this paper, we discuss the low-temperature magnetic properties of Cr2TeO6 systems where both intra-layer and inter-layer exchange couplings are antiferromagnetic, i.e. . Using linear spin-wave theory we obtain the magnon dispersion, sublattice magnetization, two-magnon density of states, and longitudinal spin–spin correlation function.

Unusual Stabilization of Dication Diradical Intermediate of Dizinc(II) Porphyrin Dimer

We have demonstrated here how the nature of a metal ion controls the reactivity of a metalloporphyrin π‐cation radical. One‐electron oxidations of diethylpyrrole‐bridged dicopper(II) and dipalladium(II) porphyrin dimers using iodine as an oxidant result in the formation of strongly interacting cofacial mixed‐valent π‐cation radical dimers. The mixed‐valent cation radical so generated being highly reactive drives a spontaneous and rapid transformation to form an indolizinium‐fused chlorin‐porphyrin heterodimer. In sharp contrast to this, similar addition of iodine leads to 1e‐oxidation of dizinc(II) porphyrin dimer, which is followed by a second oxidation to produce a dication diradical complex. The axial coordination of iodine upon 1e‐oxidation of dizinc(II) porphyrin dimer lowers the overall oxidation potential of the system, and thereby, making the second oxidation easily accessible. This has resulted in the stabilization of a dication diradical complex, in which two porphyrin π‐cation radicals undergo electronic communication through the bridging pyrrole group. Interestingly, despite being well‐separated from each other, the two radical spins undergo strong antiferromagnetic coupling to form a diamagnetic compound. The conjugation also leads to a change in identity of the bridge, which further highlights the critical role played by the bridge in the electronic communication between the two rings. DFT calculations clearly support the experimental observations.

Ring-Oxidized Zinc(II) Phthalocyanine Cations: Structure, Spectroscopy, and Decomposition Behavior.

A bromonium oxidizing agent was used to produce a ring-oxidized zinc phthalocyanine (PcZn), [PcZn(solvent)]•2[BArF4]2 (1·solvent), in good yield. This material is dimeric in the solid state with one axially coordinated solvent [tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME)] and close intradimer ring-ring distances of 3.18 and 3.136 Å (THF and DME respectively); this proximity facilitates strong antiferromagnetic coupling to yield diamagnetic dimers. 1·THF is present in solution as a monomer and a dimer. In CH2Cl2, the dimer is favored above 0.1 mM, and it is almost exclusively present in solvents with a high dielectric constant such as acetonitrile. The material 1·THF/DME decomposes in DME to a meso-nitrogen-protonated species, [HPcZn(DME)2][BArF4] (2), which was isolated and represents the first example of such a structurally characterized, protonated, unsubstituted PcM complex. A partially oxidized dimer or "pimer" [(PcZn(DME))2]•[BArF4] (3) was also structurally characterized and has a intradimer ring-ring distance of 3.192 Å, similar to 1·THF/DME. Dimer 3 also represents the first isolated PcM-based pimer. Electron paramagnetic resonance analysis of a 1.0 mM solution of 1·DME in DME showed the production of 3 over hours by the combination of 1·DME and 2 in solution.

Structure and Magnetic Properties of a 2D Paddle‐wheel Dinuclear[Cu2] Cluster‐based Polymer with 1,1‐Cyclohexanediacetate Ligand

One new two‐dimensional (2D) CuII polymer [Cu(CHDA)(H2O)]n (1) was synthesized solvothermally based on 1,1‐cyclohexanediacetic acid (H2CHDA) ligand. Single‐crystal X‐ray diffraction analysis reveals that 1 has a 2D framework structure consisting of paddle‐wheel dinuclear [Cu2] cluster unit and CHDA2– connector, which bears a 4‐connected sql network with Schläfli symbol of (44.62). Magnetic studies indicate the presence of strong antiferromagnetic coupling (J = –302 cm–1) between the two CuII ions in the paddle‐wheel dicopper(II) entity.

Interplay of covalency, spin-orbit coupling, and geometric frustration in the d3.5 system Ba3LiIr2O9

The electronic and magnetic properties of ${d}^{3.5}$ iridate ${\mathrm{Ba}}_{3}{\mathrm{LiIr}}_{2}{\mathrm{O}}_{9}$ have been studied using first-principles electronic structure calculations. The results of the calculations reveal that the system lies in an intermediate spin-orbit coupling (SOC) regime. There is strong covalency of $\mathrm{Ir}\ensuremath{-}5d$ and $\text{O}\ensuremath{-}2p$ orbitals. SOC, together with covalency, conspires to reduce the magnetic moment at the Ir site. By calculating the hopping interactions and exchange interactions, it is found that there is strong antiferromagnetic intradimer coupling within an ${\mathrm{Ir}}_{2}{\mathrm{O}}_{9}$ unit and other antiferromagnetic interdimer interactions make the system frustrated. The anisotropic magnetic interactions are also calculated. The calculations reveal that the magnitude of the Dzyaloshinskii-Moriya interactions parameter is small for this system. The magnetocrystalline anisotropy energy is large for this system and the easy axis lies on the $ab$ plane.

Directed synthesis and magnetic properties of a hexanuclear ferric cluster

The hexanuclear iron(III) complex, [Fe6(µ3-3-bpp)4(µ3-O)2(µ2-OMe)3.67(µ2-OH)0.33Cl2]·0.33MeOH·H2O (1) was synthesized by a redox reaction between FeCl2, AgNO2, and 3-H2bpp in methanol (3-H2bpp = 2,6-bis(3-pyrazolyl)pyridine). The crystal structure of the complex is composed of two trinuclear subunits related by an inversion operation. This symmetry results in an overall octahedral arrangement of Fe(III) sites within the cluster. The four equatorial Fe sites are linked together by µ2-OMe− and µ2-OH− bridges, while each of the four 3-bpp2− bridges spans two axial and one equatorial Fe sites. The two Cl− ligands cap the axial Fe sites. The difference in the coordination environment for the equatorial and axial Fe sites is validated by the observation of two quadrupole doublets in the Mössbauer spectrum of 1, which also confirms that all metal sites correspond to the high-spin Fe(III) ions. Temperature-dependent magnetic susceptibility data reveal strong antiferromagnetic exchange coupling between the Fe(III) centers, which is also justified by quantum-chemical calculations at the density-functional level of theory.

A Dimeric η1 ,η5 -Germole Dianion Bridged Titanium(III) Complex with a Multicenter Ti-Ge-Ge-Ti Bond.

Dimeric germole dianion bridged TiIII and ZrIV complexes have been synthesized. In these complexes, the germole dianion adopts a formal η1 ,η5 coordination to the two metal centers. The bonding situation in these bridged dimers is dominated by a covalent Ge-Ge interaction that results, for example, in a strong antiferromagnetic coupling of the d1 Ti centers.

A Dimeric η1,η5‐Germole Dianion Bridged Titanium(III) Complex with a Multicenter Ti−Ge−Ge−Ti Bond

AbstractDimeric germole dianion bridged TiIII and ZrIV complexes have been synthesized. In these complexes, the germole dianion adopts a formal η1,η5 coordination to the two metal centers. The bonding situation in these bridged dimers is dominated by a covalent Ge−Ge interaction that results, for example, in a strong antiferromagnetic coupling of the d1 Ti centers.

Tuning the Condensation Degree of {FeIIIn} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents.

Trinuclear μ3-oxo-centered iron(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron(III) oxo-hydroxo condensation products, isolated as (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1), [Fe12O4(OH)2(teda)4(N3)4(MeO)4]N3(NO3)0.5(MeO)0.5·2.5(H2O) (2), [Fe12O6(teda)4Cl8]·6(CHCl3) (3), [Fe22O16(OH)2(O2CCHMe2)18(bdea)6(EtO)2(H2O)2]·2(EtOH)·5(MeCN)·6(H2O) (4), and [Fe22O14(OH)4(O2CCHMe2)18(mdea)6(EtO)2(H2O)2](NO3)2·EtOH·H2O (5), where tedaH4 = N, N, N', N'-tetrakis(2-hydroxyethyl)ethylenediamine; thmeH3 = 1,1,1-tris(hydroxymethyl)ethane; mdeaH2 = N-methyldiethanolamine; and bdeaH2 = N-butyldiethanolamine. Complete carboxylate metathesis in the {Fe3} precursor complexes by thme3- or teda4- and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe6} product (1) in MeCN/CH2Cl2 or {Fe12} complexes (2 and 3) in MeOH/EtOH and CHCl3/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that 1 contains a [Fe6O(thme)4Cl6]2- cluster anion with a Lindqvist-type {Fe6(μ6-O)} core motif, charge-compensated by two protonated mdeaH3+ cations. 2 comprises a [Fe12O4(OH)2(teda)4(N3)4(MeO)4]2+ cation with a {Fe12O4(OH)2}26+ core, whereas 3 contains a charge-neutral [Fe12O6(teda)4(Cl)8] complex with an {Fe12O6}24+ core. Finally, employing flexible bdeaH2 or mdeaH2 ligands under soft reaction conditions afforded giant {Fe22} oxo-hydroxo complexes (4 and 5) with a central {Fe6} layer sandwiched between two outer {Fe8} groups. Magnetic studies of 1-5 revealed strong antiferromagnetic coupling between the FeIII spin centers in all clusters.

Study on adjacent radicals short contact interaction, spin density, overlap integral and strong anti-ferromagnetic coupling strength

Through theoretical calculations and magnetostructural study of nine radical compounds that exhibit strong anti-ferromagnetic coupling strength, it is revealed preliminarily that the overlap integral between adjacent radicals short contact atoms is relevant to associated strong anti-ferromagnetic coupling strength. It is also confirmed that spin density and overlap integral between adjacent radical short contact atoms are the two major factors that dominate intermolecular strong anti-ferromagnetic coupling strength. The study also reveals that the factor of the overlap integral can replace the factors of both interatomic short contact distance and slippage degrees of π-π stacking. The study also reveals for the first time that the overlap integral changes with different short contact atom and different central coordinated atom.

On the Border between Low-Nuclearity and One-Dimensional Solids: A Unique Interplay of 1,2,4-Triazolyl-Based {CuII5(OH)2} Clusters and MoVI-Oxide Matrix.

A pentanuclear CuII5-hydroxo cluster possessing an unusual linear-shaped configuration was formed and crystallized under hydrothermal conditions as a result of the unique cooperation of bridging 1,2,4-triazole ligand ( trans-1,4-cyclohexanediyl-4,4'-bi(1,2,4-triazole) ( tr2 cy)), MoVI-oxide, and CuSO4. This structural motif can be rationalized by assuming in situ generation of {Cu2Mo6O22}4- anions, which represent heteroleptic derivatives of γ-type [Mo8O26]4- further interlinked by [Cu3(OH)2]4+ cations through [ N- N] bridges. The framework structure of the resulting compound [Cu5(OH)2( tr2 cy)2Mo6O22]·6H2O (1) is thus built up from neutral heterometallic {Cu5(OH)2Mo6O22} n layers pillared with tetradentate tr2 cy. Quantum-chemical calculations demonstrate that the exclusive site of the parent γ-[Mo8O26]4- cluster into which CuII inserts corresponds with the site that has the lowest defect ("MoO2 vacancy") formation energy, demonstrating how the local metal-polyoxomolybdate chemistry can express itself in the final crystal structure. Magnetic susceptibility measurements of 1 show strong antiferromagnetic coupling within the Cu5 chain with exchange parameters J1 = -500(40) K (-348(28) cm-1), J2 = -350(10) K (-243(7) cm-1) and g = 2.32(2), χ2 = 6.5 × 10-4. Periodic quantum-chemical calculations reproduce the antiferromagnetic character of 1 and connect it with an effective ligand-mediated spin coupling mechanism that comes about from the favorable structural arrangement between the Cu centers and the OH-, O2-, and tr2 cy bridging ligands.

A multi-state synthetic ferrimagnet with controllable switching near room temperature

Ferrite composites with temperature-induced magnetization reversal, and synthetic ferrimagnets and antiferromagnets have been of great interest to the scientific community due to their uncommon thermal properties and potential applications in magnetic storage, spintronic devices, and several other fields. One of the advantages of these structures is the strong antiferromagnetic coupling, which stabilizes the magnetization state and gives access to interesting static and dynamical magnetic behaviors. Some of their drawbacks lie in that it is difficult to induce temperature-induced magnetization reversal at room temperature in composites, and that the strong interaction makes it difficult to induce a parallel magnetization state (and thus a high magnetic moment). In this work, we study numerically the magnetization behaviour of a Cu(1 0 0)/Ni/Pt/[Co/Pt]4 synthetic ferrimagnet and show that is possible to revert the sign of its magnetization by varying the temperature in ranges around room temperature. We also show that the four parallel and antiparallel magnetization states are stable at temperatures up to 360 K, and demonstrate that it is possible to change deterministically between these states by increasing the temperature of the device and/or applying a magnetic field, showcasing simultaneous non-hysteretic and hysteretic switching processes induced by temperature. Thus, this structure opens the possibility to have reconfigurable magnetic devices with multiple purposes based on the nature of the different switching events and the interplay between them.

Imposing long-range ferromagnetic order in rare-earth-doped magnetic topological-insulator heterostructures

The combination of topological properties and magnetic order can lead to new quantum states and exotic physical phenomena, such as the quantum anomalous Hall (QAH) effect. The size of the magnetic gap in the topological surface states, key for the robust observation of the QAH state, scales with the magnetic moment of the doped three-dimensional topological insulator (TI). The pioneering transition-metal doped $({\mathrm{Sb},\mathrm{Bi})}_{2}({\mathrm{Se},\mathrm{Te})}_{3}$ thin films only allow for the observation of the QAH effect up to some 100 mK, despite the much higher magnetic ordering temperatures. On the other hand, high magnetic moment materials, such as rare-earth-doped $({\mathrm{Sb},\mathrm{Bi})}_{2}({\mathrm{Se},\mathrm{Te})}_{3}$ thin films, show large moments but no long-range magnetic order. Proximity coupling and interfacial effects, multiplied in artificial heterostructures, allow for the engineering of the electronic and magnetic properties. Here, we show the successful growth of high-quality Dy:${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$/Cr:${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ thin film heterostructures. Using x-ray magnetic spectroscopy we demonstrate that high transition temperature Cr:${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ can introduce long-range magnetic order in high-moment Dy:${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$---up to a temperature of 17 K---in excellent agreement with first-principles calculations, which reveal the origin of the long-range magnetic order in a strong antiferromagnetic coupling between Dy and Cr magnetic moments at the interface extending over several layers. Engineered magnetic TI heterostructures may be an ideal materials platform for observing the QAH effect at liquid He temperatures and above.

Multiferroic and magneto-dielectric properties in Fe doped BaTiO3

Polycrystalline barium titanate (BTO) samples doped with infinitesimal quantity of iron separately and simultaneously in both A and B sites are prepared using solid state reaction method with an emphasis on its site preference. Structural studies establish the transformation from tetragonal to pseudo-cubic phase upon changing the dopant site. An appreciable compressive lattice strain is induced when Fe is doped in the A-site while it becomes tensile and negligibly small when Fe occupies B-site. Further, the suppression of 308 cm−1 band in the Raman spectra highlights the coexisting cubic and tetragonal phases in A-site doped BTO. Ferroelectric ordering is validated using P–E loop and PUND (positive up and negative down) measurements. Dielectric constant undergoes a transition from ferroelectric to paraelectric state at 388 K for BTO and it varies with occupation site of Fe. Low temperature magnetic measurements reveal the strong antiferromagnetic coupling in A-site doped BTO sample. Magneto-dielectric measurements portray the proper choice of doping site in BaTiO3 so as to introduce multiple magnetic and electric states in it.

L10 Fe−Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions

Magnetic materials that possess large bulk perpendicular magnetic anisotropy (PMA) are essential for the development of magnetic tunnel junctions (MTJs) used in future spintronic memory and logic devices. The addition of an antiferromagnetic layer to these MTJs was recently predicted to facilitate ultra-fast magnetization switching. Here, we report a demonstration of a bulk perpendicular synthetic antiferromagnetic (P-SAFM) structure comprised of a (001) textured FePd/Ru/FePd trilayer with a face-centered-cubic (fcc) phase Ru spacer. The L10 FePd P-SAFM structure shows a large bulk PMA (~10.2 Merg/cc) and strong antiferromagnetic coupling (~2.60 erg/cm2). Full perpendicular magnetic tunnel junctions (P-MTJs) with a L10 FePd P-SAFM layer are then fabricated. Tunneling magnetoresistance ratios of up to ~25% (~60%) are observed at room temperature (5K) after post-annealing at 350 C. Exhibiting high thermal stabilities and large Ku, the bulk P-MTJs with an L10 FePd P-SAFM layer could pave a way for next-generation ultrahigh-density and ultra-low-energy spintronic applications.

Magnetic Sponge Behavior via Electronic State Modulations.

A reversible magnetic change in response to external stimuli is a desired function of molecular magnetic materials. The magnetic change induced by a change in the intrinsic spin is significant because the magnetic change is inevitable and could become drastic. In this study, we demonstrate a reversible magnetic change closely associated with electronic state modulations, as well as structural modifications realized by solvation/desolvation cycles of a magnetic sponge. The compound was a D2A-type layered magnet, [{Ru2(O2CPh-2,3,5-Cl3)4}2(TCNQMe2)]·4DCM (1; 2,3,5-Cl3PhCO2- = 2,3,5-trichlorobenzoate; TCNQMe2 = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane), where [Ru2(O2CPh-2,3,5-Cl3)4] ([Ru2II,II]) is an electron donor (D) and TCNQMe2 is an electron acceptor (A). Compound 1 had a one-electron-transferred, charge-ordered state with a [{Ru2II,II}-TCNQMe2•--{Ru2II,III}+] (1e-I) formula. Strong intralayer antiferromagnetic couplings between [Ru2II,II] with S = 1 or [Ru2II,III]+ with S = 3/2 and TCNQMe2•- with S = 1/2, as well as ferromagnetic interlayer interactions, induced long-range ferrimagnetic ordering at Tc = 101 K. Interstitial DCM molecules were located between layers, and these were gradually eliminated under vacuum at 80 °C to form a solvent-free compound (1-dry) without loss of crystallinity. The electronic state of 1-dry thermally fluctuated and eventually provided a charge-disproportionate disordered state, with a [{Ru2}0.5+-TCNQMe21.5--{Ru2II,III}+] (1.5e-I) formula as the ground state. The Tc in 1-dry was 34 K because of the presence of diamagnetic TCNQMe22- in some parts of the framework. A large Tc variation with Δ Tc ≈ 70 K was switchable; switching was achieved by charge-state modulations accompanied by subtle structural modifications in solvation/desolvation treatments.

Tuning of optical mode magnetic resonance in CoZr/Ru/CoZr synthetic antiferromagnetic trilayers by oblique sputtering

CoZr/Ru/CoZr synthetic antiferromagnetic trilayers with strong antiferromagnetic interlayer coupling were fabricated by an oblique sputtering method that induced in-plane uniaxial magnetic anisotropy. A microstrip method using a vector network analyzer was applied to investigate the magnetic resonance modes of the trilayers, including the acoustic modes (AMs) and the optical modes (OMs). At zero magnetic field, the CoZr/Ru/CoZr trilayers showed OMs with resonance frequencies of up to 7.1 GHz. By increasing the applied external magnetic field, the magnetic resonance mode can be tuned to various OMs, mixed modes, and AMs. Additionally, the magnetic resonance mode showed an angular dependence between the magnetization and the microwave field, which showed similar switching of the magnetic modes with variation of the angle. Our results provide important information that will be helpful in the design of multifunctional microwave devices.