Curie-Weiss Plot Research Articles

Investigation of the structure, optical and magnetic properties of the honeycomb layered Na3(MnIIM)SbO6 (M (II) = Fe, Co, Ni, Zn, Mg) and Na3(FeIIM′)SbO6 (M′ (II) = Co, Ni, Zn, Mg) oxides

Rock salt superstructured oxides synthesized through conventional high temperature methods have been shown to accommodate Mn2+ and Fe2+ ions leading to the formation of Na3(MnM)SbO6 (M (II) = Fe, Co, Ni, Zn, Mg) and Na3(FeM')SbO6 (M′ (II) = Co, Ni, Zn, Mg) oxides. The layered structures (in S. G. C2/m) consist of honeycomb arrays formed by the 2:1 ordering of (Mn, M)2+, Sb5+ and (Fe, M′)2+, Sb5+ cations and are interleaved by the Na+ cations. PXRD measurements do not show any evidence for additional superstructure formation, and the unit cell volumes confirm a linear variation with the average ionic radii of the divalent cations. Diffuse reflectance measurements exhibit the characteristic d-d transitions from the optically active combination of transition metal ions in the solid solution members. Dilution of Mn2+ (d5) ions by M = Co, Ni, Zn resulted in typical paramagnetic behavior (300–100 K), with definite AFM ordering (below 8 K) and negative Weiss (θ) constants as shown by the magnetic susceptibility measurements of Na3(MnM)SbO6 oxides. The divergence between the ZFC and FC values is absent (at 0.1 T) in the solid solution members, unlike the parent Na3Mn2SbO6. Na3(MnMg)SbO6 alone differed and registered only a negative θ without any AFM ordering. All of the corresponding Na3(FeM')SbO6 (M′ = Co, Ni, Zn, Mg) oxides exhibited definite AFM ordering with negative θ values indicating a ground state with dominant AFM interactions. The exception has been the Co2+ substituted sample showing a positive θ (20 K) value from the Curie-Weiss plot, suggesting ferromagnetic interactions. The reported low dimensional oxides derived by combining divalent metal ions in the honeycomb geometry provide scope for studying the exciting aspects of solid state chemistry and physics. Similarly, the green emission observed from the PL measurements in the oxides containing Mn2+ reveals the prospects of developing novel phosphor materials.

Exotic magnetic properties and enhanced magnetoelectric coupling in Fe3O4-BaTiO3 heterostructures

In the present work, magnetoelectric composites of Fe3O4 and BaTiO3 were successfully synthesized with 0–3 and 1–3 connectivity. In Fe3O4-BaTiO3 composites with 1–3 connectivity, the M-H loop analysis shows the presence of the isotropic point, whereas the M-T measurements of both samples reveal a unique downturn anomaly in the Curie-Weiss plot, indicating the presence of a Griffiths-like phase. The cluster glass nature of Fe3O4 nanostructures leads to the formation of exchange bias in the investigated ME composites. The different phase transitions of BaTiO3 are visible in the M(T) data as a consequence of magnetoelectric coupling between Fe3O4 and BaTiO3. The maximum magnetoelectric coupling coefficients observed for the Fe3O4-BaTiO3 composites with 0–3 and 1–3 connectivity are 8.34 mV cm−1 Oe−1 and 28.78 mV cm−1 Oe−1, respectively; both values are higher than that of the previously reported values of Fe3O4-BaTiO3 composites. Further, the magnetoelectric coupling coefficients of Fe3O4-BaTiO3 1–3 composites show an increasing trend towards the BaTiO3 rich phase.

Non-ferroelectric relaxor properties of BMN, Bi3.55Mg1.78Nb2.67O13.78 pyrochlore

Phase-pure Bi3.55Mg1.78Nb2.67O13.78, BMN pyrochlore was prepared by conventional solid-state reaction at 1025 °C for 2–3 days. Electrical properties measured by impedance spectroscopy over the range 10–1073 K showed relaxor behaviour with a maximum dielectric constant, ε′max of 209 at its temperature maximum, Tmax of 204 K. Impedance data were analysed by fixed-frequency sweeps of dielectric constant and tan δ and variable frequency scans at fixed temperature. Low temperature data were modelled using the classic dielectric relaxation circuit that consists of a resistance in combination with series and parallel capacitances, but modified to include a constant phase element that introduced variable resistances and capacitances into the equivalent circuit. There was no evidence of ferroelectric behaviour, either from extrapolation of high temperature Curie-Weiss plots or the temperature-dependence of low temperature capacitance data. At intermediate temperatures, ∼240–623 K, BMN is an insulator with resistivity >10 MΩ cm. Above ∼623 K, it is a modest electrical conductor, activation energy 1.07 eV; the charge carriers are probably oxide ions.

Effect of Bi-functional Hierarchical Flower-like CoS Nanostructure on its Interfacial Charge Transport Kinetics, Magnetic and Electrochemical Behaviors for Supercapacitor and DSSC Applications

Metal sulfides are of great interest for future electrode materials in supercapacitor and solar cell applications owing to their superior electrochemical activity and excellent electrical conductivity. With this scope, a binary transition metal sulfide (CoS) is prepared via one-step hydrothermal synthesis. Hexagonal phase of CoS with space group of P63/mmc(194) is confirmed by XRD analysis. Additional cubic Co3S4 phase in the prepared sample originates the mixed valence state of Co (Co2+ and Co3+) is affirmed from XPS analysis. Morphological features are visualized using HRSEM images that shows nanoflower shaped star-anise structure. Employing the prepared CoS as active electrode material, interfacial charge transport kinetics is examined by EIS-Nyquist plot. The supercapacitive performances are tested in two and three-electrode system which exhibited respective specific capacitances of 57 F/g and 348 F/g for 1 A/g. Further, the fabricated asymmetric CoS//AC supercapacitor device delivers an appreciable energy density of 15.58 Wh/kg and power density of 700.12 W/kg with excellent cyclic stability of 97.9% and Coulombic efficiency of 95% over 2000 charge-discharge cycles. In addition, dye-sensitized solar cells are fabricated with CoS counter electrode and the obtained power conversion efficiency of 5.7% is comparable with standard platinum based counter electrode (6.45%). Curie-Weiss plot confirms the transition of paramagnetic nature into ferrimagnetic behavior at 85 K and Pauli-paramagnetic nature at 20 K respectively. Temperature dependent resistivity plot affirms the metallic nature of CoS sample till 20 K and transition to semiconducting nature occurs at <20 K owing to Peierl’s transition effect.

Structural, magnetic and dielectric properties of the novel magnetic spinel compounds ZnCoSnO4 and ZnCoTiO4

The transparent semiconductor Zn2SnO4 with cubic spinel structure and the isostructural Zn2TiO4 have been magnetically doped with Co2+. ZnCoSnO4 and ZnCoTiO4 exhibit ferrimagnetism below TN ≈ 13 K and TN ≈ 17 K. Ferrimagnetic moments are evident in M vs H curves below TN by small hysteresis. Fits to strictly linear Curie-Weiss plots above TN give μeff ≈ 4.86 μB and ≈4.91 μB for ZnCoSnO4 and ZnCoTiO4, above theoretical predictions. Impedance spectroscopy data from sintered ceramic can be fitted with a standard equivalent circuit model based on two RC elements for bulk and GB areas. The relative dielectric permittivity of the bulk is ≈20 and ≈30 for Zn2SnO4 and Zn2TiO4. The semiconducting ZnCoSnO4 and ZnCoTiO4ceramics exhibit bulk resistivity of ≈1 106 Ω cm and ≈1 105 Ω cm at 560 K (287 °C), and bulk activation energies of EA ≈ 1.2 eV and 1.1 eV.

Evolution of structure and magnetic properties of stoichiometry and oxygen rich LaMnO3 nanoparticles

In this report, the evolution of structure and magnetic properties in stoichiometry and oxygen rich LaMnO3 samples synthesized by a simple, cost effective, conventional co-precipitation technique are systematically studied. While X-ray powder diffraction reveals a monoclinic, I2/a structure in both samples, Reitveld refinement demonstrates higher John-Teller (J-T) distortion in the former one. Higher J-T distortion is accompanied with a large deviation in MnO bond length. FESEM (Field Emission Scanning Electron Microscopy) analysis combined with crystallite size calculated from XRD peak profile suggest that the particles are of 50–60nm and are polycrystalline in nature. The antiferromagnetism observed in bulk LaMnO3 with TN=140K evolves towards a ferromagnetic order in both stoichiometry and oxygen rich samples. However, Curie temperature, TC, is found to be higher in oxygen rich sample due to higher MnOMn bond angle. The large effective magnetic moment calculated from Curie-Weiss plot is found to be higher in stoichiometry sample. Higher moment is ascribed to high oxygen vacancies evidenced from XPS analysis. Dispersion behavior observed in frequency dependent ac susceptibility (χ) indicates the spin-glass, cluster-glass and interacting superparamagnetic behavior. Fitting the susceptibility data with phenomenological models such as Neel-Arrhenius, Vogel-Fulcher and Power law, while canonical spin-glass, cluster-glass and interacting superparamagnetism is ruled out, the spin-glass behavior with a higher relaxation time in oxygen rich sample is confirmed.

Structural and magnetic properties of chemically synthesized dilute magnetic semiconducting (In0.9Fe0.1)2O3 nanoparticles

at.% Fe doped In2O3 dilute magnetic semi- conducting (DMS) nanoparticles are synthesized using low temperature 'pyrophoric reaction processes'. X-ray dif- fraction studies at room temperature have revealed single- phase cubic bixbyite structure of the sample. Nano size grain distribution has been observed by FESEM. The recorded temperature dependent magnetization curve exhibits concave nature in the low temperature range for both FC and ZFC conditions revealing insulating DMS like behavior. No phase transition has been noticed within the studied temperature range. Study of magnetic properties in detail confirms the weak ferromagnetic ordering along with paramagnetic behavior of the nanometric sample. From the temperature dependence of inverse magnetic susceptibility (χ −1 (T)) using Curie-Weiss plot, the effective Bohr mag- neton (μeff) has been estimated to be ~3.715 μB/Fe ion. Observed photoluminescence spectrum of Fe doped In2O3 nanostructures mainly results from the recombination of electrons occupying oxygen vacancies or Fe 3+ ions with photo-excited holes.

Heterometallic, Hybrid, Heavy Main‐Group Iodometallates Containing Lanthanide Complexes: Template Synthesis, Structures, Thermal, Optical, Luminescent and Magnetic Properties

AbstractUsing [Ln(L)8]3+ [Ln = Tb, Y; L = dimethyl sulfoxide (DMSO), N,N‐dimethylformamide (DMF)] cations as templating reagents, the syntheses and crystal structures of the following new metal organic–inorganic hybrid complexes based on either discrete clusters or 1D chains of an iodoplumbate or‐bismuthate moiety are reported: [Tb(DMSO)8]2[(DMSO)2Pb5I16] (1), [Tb(DMF)8][Pb3I9]1∞·DMF (2) and [Ln(DMF)8][Bi2I9] [Ln = Y (3), Tb (4)]. These derivatives were characterized by thermogravimetric analysis (TGA), diffuse‐reflectance spectroscopy, luminescence spectroscopy and magnetic studies. TGA studies show that the thermal stability of these complexes decreases in the order 2 &gt; 3 ≈ 4 &gt; 1. An optical band‐gap in the range 1.90–2.15 eV in the diffuse‐reflectance spectra of 1–4 indicate their potential use as semiconductors, 3 and 4 being the most promising because of their low band gap values. Compared to the precursors [Tb(DMSO)8]I3 and [Tb(DMF)8]I3, the high energy transitions in the excitation spectra of 1, 2 and 4 are quenched by a process that is best attributed to the autoionization of the carriers in the material. The temperature dependence of the magnetic susceptibilities of 1, 2 and 4 was reproduced well by a Curie–Weiss plot at 2–300 K.

Magnetic properties of ErN films

We report a magnetization study of stoichiometric ErN nanocrystalline films grown on Si and protected by a GaN passivating layer. According to the temperature dependence of the resistivity the films are heavily doped semiconductors. Above 100 K the magnetization data fit well to a Curie–Weiss behavior with a moment expected within the free-ion Er 3 + J = 15 2 multiplet. Below 50 K the Curie–Weiss plot steepens to an effective moment corresponding to that in the crystal-field determined quartet ground state, and develops a clear paramagnetic Curie–Weiss temperature of about 4.5 K. Zero-field- and field-cooled magnetization curves and the AC susceptibility firmly establish a ferromagnetic ground state within that multiplet below a Curie temperature of 6.3 ± 0.7 K . Due to the (1 1 1) texture of the film the comparison between the magnetization behavior, when the field is applied parallel and perpendicular to the film plane, gives new information about the magnetic structure. An arrangement of the moments according to the model derived from neutron diffraction for bulk HoN is strongly suggested.

Giant pyroelectric coefficient of Mn-doped PLT thin films epitaxially grown on (001) Pt/MgO

The c-axis-oriented epitaxial thin films of Mn-doped Pb 1− x La x Ti 1− x/4 O 3 (PLT) on (001) Pt/MgO substrates were prepared by rf-magnetron sputtering. To investigate the effect of the doped ion, 0–1.7 mol% MnO 2 added to the PLT target powder. The temperature dependence of the relative dielectric constant ɛ r measurements and modified Curie–Weiss plots suggested that the increasing of diffuseness n was induced by high-La substitution and the diffuseness n of PLT thin films decreased by the addition of Mn, considerably. Inner stress and thermodynamic analysis were carried out and the results propose that the increasing of γ with Mn doping caused by increasing the misfit strain of the c-axis-oriented epitaxial PLT thin films and substrate. As a result, giant pyroelectric coefficient ( γ = 15.8 × 10 −8 C/cm 2 K) of Mn-doped epitaxial PLT thin film was achieved.

Fe(III)-montmorillonite: Basic properties and diffusion of tracers relevant to alteration of bentonite in deep geological disposal

In the deep geological repository of high-level nuclear waste (HLW), the interaction of carbon steel (Fe) overpack container and the back-fill clay mineral, montmorillonite (mont), is an important issue to be clarified in view of the long-term performance of clay mineral as an engineered barrier. To arrive at some understanding of the altered clay at the Fe/clay interface, Fe(III)-mont is used here for preliminary investigation to see if there is any considerable difference in the basic properties, mainly diffusion of tracers with respect to Na-mont, although Fe(III)-mont is not a realistic analogue of altered clay in the reducing chemistry conditions anticipated in the subsurface of HLW, unlike Fe(II)-mont which is difficult to prepare and handle in the ambient atmosphere due to its gradual oxidation. Fe(III)-mont was prepared by the conventional cation exchange method with 0.4 M FeCl 3 solution. The total Fe(III) ions adsorbed was about 1.42 meq/g, while the CEC of parent clay was 1.2 meq/g. Thus ∼ 18% excess Fe(III) ions were present presumably as iron oxy hydroxide, i.e., about 2 wt.% with respect to FeOOH or Fe(OH) 3 in the bulk sample. The sample was further characterized by X-ray diffraction (XRD), infrared (IR), thermogravimetry, magnetization, and the methylene blue (MB) adsorption. From these conventional techniques, the minor Fe-oxide phase associated with the Fe(III)-mont could not be detected, although we cannot rule out its existence. The paramagnetic behavior of Fe(III)-mont was evident from the Curie–Weiss plot (300 K down to 5 K). Some basic properties like osmotic swelling, diffusion of tracers and thermal stability are evaluated here. The osmotic swelling of Fe(III)-mont was very low, ∼ 5 ml/g, while that of Na-mont was > 40 ml/g. Apparent diffusion coefficient ( D a) of tracers viz., 22Na +, HTO and 36Cl − was determined using compacted (dry density, ρ d = 1.0, 1.6 Mg m − 3 ), water-saturated Fe(III)-mont. There was no considerable change in D a of these tracers in Fe(III)-mont when compared to that in Na-mont, in spite of higher pore water availability in Fe(III)-mont due to reduced swelling. For instance at ρ d = 1.6 and 25 °C, D a (×10 − 11 m 2/s) of 22Na + (2.6) was same as that in Na-mont whereas D a of HTO (11.4) and 36Cl − (1.0) have varied marginally. For comparison, the corresponding D a (×10 − 11 m 2/s) values in Na-mont were 2.7, 7.2 and 3.4, respectively. Also, at ρ d = 1.6, the diffusion activation energy ( E A, kJ mol − 1 ) of HTO (17.5) in Fe(III)-mont was comparable to that in free water, however, E A of 36Cl − (13.1) was remarkably low, which may be ascribed to the so-called ‘anion exclusion’ effect. Furthermore, thermal stability of Fe(III)-mont indicated the existence of interlayer Fe(III) in the ionic state up to ∼ 190 °C, based on the XRD and MB adsorption test. On heating to > 200 °C, irreversible dehydration of interlayer cations occurred, and the chemisorption of NH 3 indicated two distinct acid sites at about 300 °C and 600 °C.

A Perimidine-Derived Non-Kekulé Triplet Diradical

6,9-Di(tert-butyl)-1-methyltetrazolo[1,5-a]perimidine (1) has been synthesized from naphthalene in seven steps. The EPR spectra, recorded after irradiation of 1 in a butyronitrile matrix at 77 K (lambda = 351 nm) and in Ar and Xe matrixes at 4.6 K (lambda > or = 345 nm), showed a six-line, high-field signal (Delta m(S) = +/- 1), centered at 3350 G in butyronitrile, along with a half-field signal (Delta m(S) = +/- 2), which is characteristic for triplets. Simulation of the observed EPR spectra gave values for the zero-field splitting parameters of |D/hc|/cm(-1) = 0.0105, |E/hc|/cm(-1) = 0.0014 in butyronitrile and |D/hc|/cm(-1) = 0.0107, |E/hc|/cm(-1) = 0.0016 in Ar. These EPR parameters are consistent with the diradical 5,8-di(tert-butyl)-2-(N-methylimino)perimidine-1,3-diyl ((3)2) as source of the EPR spectra. Linearity of the Curie-Weiss plot and UB3LYP and (14/14)CASPT2 calculations of the singlet-triplet energy difference (DeltaE(ST) approximately 8-10 kcal/mol) indicate that the triplet is the ground state of 2, as predicted for such a nondisjoint diradical.

Epitaxial growth and magnetic properties of GaMnNAs

The influence of the nitrogen doping in GaMnAs on the magnetic properties was investigated. The GaMnNAs film was grown by molecular beam epitaxy with a nitrogen plasma source. The GaMnNAs film with a large amount of nitrogen showed super-paramagnetic behaviour. The Arrott-plot and the Curie–Weiss plot also support the paramagnetism. The high concentration of nitrogen caused suppression of the ferromagnetism. One of the possibilities of the suppression is due to the band gap bowing effect, which causes the anti-bonding state of 3d-Mn to locate in the valence band in high nitrogen concentration.

Crystallography and magnetism of 3-(N-tert-butyl-N-aminoxyl)benzoic acid

3-(N-tert-Butyl-N-aminoxyl)benzoic acid is a stable red solid that crystallizes to form chains of nitroxide to aryl CH contacts, with the pairs of such antiparallel chains joined by complementary carboxylic acid two-point hydrogen bonds. Although it strongly adsorbs to silica gel, it does not show solution phase ESR evidence of discrete triplet state radical pairing. Solid-state magnetic susceptibility studies show antiferromagnetic downturn at lower temperatures, with a change in slope at about 10 K in Curie–Weiss plots. The results suggest either a phase change at low temperatures, or the presence of multiple competing exchange interactions.

Understanding Thickness Effects in Thin Film Capacitors

Pulsed Laser Deposition (PLD) was used to make Au/(Ba0.5Sr0.5)TiO3/(La0.5Sr0.5) CoO3/MgO thin film capacitor structures. Functional properties were studied with changing BST thickness from ∼1265 nm to ∼63 nm. The dielectric constant was found to decrease, and migration of T m (the temperature at which the dielectric constant is maximum) to lower temperatures occurred as thickness was reduced. Curie-Weiss plots of the as-obtained dielectric data, indicated that the Curie temperature was also systemmatically progressively depressed. Further, fitting to expressions previously used to describe diffuse phase transitions suggested increased diffuseness in transformation behaviour as film thickness decreased. This paper discusses the care needed in interpreting the observations given above. We make particular distinction between the apparent Curie-temperature derived from Curie-Weiss plots of as-measured data, and the inherent Curie temperature determined after correction for the interfacial capacitance. We demonstrate that while the apparent Curie temperature decreases as thickness decreases, the inherent Curie temperature is thickness independent. Thickness-invariant phase transition behaviour is confirmed from analysis of polarisation loops, and from examination of the temperature dependence of the loss-tangent. We particularly note that correction of data for interfacial capacitance does not alter the position of T m . We must therefore conclude that the position of T m is not related simply to phase transformation behaviour in BST thin films.

Magnetic and transport properties in Fe3$minus;xVxAl

We have measured DC magnetic susceptibilities and Hall resistivities for Fe 3− x V x Al with x =1.0, 0.9. The magnetic moments obtained from a Curie–Weiss plot appreciably deviated from the saturated magnetic moments obtained at 5 K suggesting that the magnetization arose from band splitting. A notable extraordinary Hall effect was observed at low temperatures. We assume that the extraordinary Hall effect arises from a side step jump owing to magnetic clusters.

Magnetic and transport properties in Fe3−xVxAl

We have measured DC magnetic susceptibilities and Hall resistivities for Fe3−xVxAl with x=1.0, 0.9. The magnetic moments obtained from a Curie–Weiss plot appreciably deviated from the saturated magnetic moments obtained at 5K suggesting that the magnetization arose from band splitting. A notable extraordinary Hall effect was observed at low temperatures. We assume that the extraordinary Hall effect arises from a side step jump owing to magnetic clusters.

Crystal structure and magnetism of layered Ln2Ca 2MnNiO 8 ( Ln=Pr, Nd, Sm, and Gd) compounds

We report the syntheses, crystal structure, and magnetic properties of a series of distorted K 2NiF 4-type oxides Ln 2Ca 2MnNiO 8 ( Ln=Pr, Nd, Sm, and Gd) in which Ln/Ca and Mn/Ni atoms randomly occupy the K and Ni sites respectively. The Ln=La compound does not form. These compounds show systematic distortions from the ideal tetragonal K 2NiF 4 structure (space group I4/ mmm) to an orthorhombic structure (space group Pccn) with buckled MO 2 ( M=Mn/Ni) layers. The degree of distortion is increased as the size of Ln decreases. Based on the magnetic data and X-ray absorption near edge spectra, we assigned Mn IV and Ni II. The Curie–Weiss plots of the high temperature magnetic data suggest strong ferromagnetic interactions probably due to Mn IV–O–Ni II linkages, implying local ordering of Mn/Ni ions to form ferromangnetic clusters in the MO 2 layers. At low temperatures below 110–130 K, these compounds show antiferromagnetic behaviors because of Mn IV–O–Mn IV and/or Ni II–O–Ni II contacts between the ferromagnetic clusters. The Ln=Pr and Nd compounds show additional antiferromagnetic signals that we attribute to the interlayer interactions between the clusters mediated by the Pr 3+ and Nd 3+ ions in the interlayer spaces. The present compounds show many parallels with the previously reported Ln 2Sr 2MnNiO 8 compounds.

Evidence for two-phase regions in Ba0.5Sr0.5TiO3 thin films from capacitance–voltage data

The Curie–Weiss plots of reciprocal dielectric constant versus temperature, in Ba0.5Sr0.5TiO3 films grown onto SrRuO3 lower electrodes by pulsed-laser deposition, show two minima below film thicknesses of 280 nm. This double minima implies possible mixed phases in the thin films. A graphical plot of capacitance for decreasing dc voltage versus that of increasing dc voltage shows a well-defined triangular shape for both Pb(Zr0.4Ti0.6)O3 and SrBi2Ta2O9 thin films. However, for a 175-nm-thick Ba0.5Sr0.5TiO3 thin film, the plot shows an overlapping of two triangles, suggesting mixed phases. This graphical method appears to be effective in detecting structural subtleties in ferroelectric capacitors.

Synthesis, crystal structures and electronic properties of imidazoline nitroxide radicals bearing active groups in electropolymerisation

Thiophene-, phenylthiophene-, and indole-based nitronyl nitroxide (NN) and imino nitroxide (IN) radicals have been synthesised and their electrochemical and magnetic properties have been studied. Cyclic voltammetry measurements show that NN radicals (1–3) exhibit a one-electron quasi-reversible oxidation process that results in the formation of the corresponding nitrosonium cations. This behaviour pushes the oxidation potential of the other redox-active moiety to very high values. The oxidation of the thiophene subunit occurs at 2.35 V, whereas the oxidation of the phenylthiophene and indole moieties takes place at 1.65 and 1.39 V, respectively. Oxidation of IN radicals (4–5) is irreversible and occurs at higher potentials, as compared to the parent NN compounds. This process has a weaker effect on the redox behaviour of the thiophene functions. Single-electron reductions are observed for all the radicals at around −1.2 V. The thiophene-based NN radical (1) crystallises in the monoclinic C2/c space group. The analysis of the crystal structure shows the formation of dimers of molecules related by a centre of symmetry. These dimers packed to form a honeycomb lattice of radicals. An estimate of the magnetic interaction between radicals in the solid (J = −3.4 K) has been obtained by fitting the magnetic susceptibility of 1 with the corresponding high-temperature series expansion. The indole-based NN radical (3) crystallises in the monoclinic P21/n space group. The crystal packing shows the presence of strong hydrogen bonds between the nitroxide oxygen atom and the hydrogen of the indolic amino function. This leads to zigzag chains that packed in the solid to form a two-dimensional squared lattice. Using the high-temperature series expansion for a 2D squared lattice of isotropic S = 1/2 spins in the fit of the magnetic susceptibility of 3 affords a value of J = −0.11 K for the interradical exchange coupling parameter. The phenylthiophene-based IN compound (5) crystallises in the triclinic P1 space group. Three independent molecules form its crystal structure. The magnetic properties of compounds 2, 4 and 5 are also indicative of weak antiferromagnetic interactions. Curie–Weiss plots for these compounds afford values of the Weiss constant θ of – 1.5, – 2.8 and – 1.9 K for 2, 4 and 5, respectively.