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Metal organic compound (C2H5NH3)2CuCl4 belongs to the family of layered perovskite multiferroic materials. It consists of ferromagnetic layers of corner sharing [CuCl4]2− octahedra connected by organic ions (two layers of [C2H5NH3]+). In this work we have studied magnetic properties of (C2H5NH3)2CuCl4 using SQUID magnetometer and AC susceptometer. Temperature dependence of magnetization showed existence of the antiferromagnetic transition at 10.2 K which changes to ferromagnetic with the application of moderate magnetic field. Near structural transition temperatures the anomaly of magnetization was observed. Hysteresis loops showed ferromagnetic behaviour for T T N and existence of anisotropy. Results of AC measurements showed no frequency dependence of the susceptibility and obtained temperature dependence of nonlinear susceptibility can be interpreted as a result of successive crossovers between different regimes.

The two red centrosymmetric Ni(II) tetrameric complexes with defective double-cubane core, [Ni2L2(H2O)]2·0.75 CH3OH (1) and [Ni2L2(CH3CN)]2 (2) (H2L = N-(2-hydroxy-5-methylphenyl)- salicylideneimine), have been isolated and magnetically characterized, emphasizing the effect of the reaction temperature on structural and magnetic properties of isolated complexes. Prevailing antiferromagnetic interactions in the complexes are observed leading to the non- magnetic ground state. Comparation with the known magneto-structural correlations in nickel cubane and dicubane complexes is discussed.

This study reports on the nature of electrical transport and role of structural changes induced by different type and content of TMO in Ag–containing glasses of xTMO–(30–0.5x)Ag2O–(30–0.5x)ZnO–40P2O5 (TMO = MoO3/WO3, 0 ≤ x ≤ 60 mol%) composition. Raman spectra show clustering of WO6 units in glasses with high WO3 content while the addition of MoO3 induces a gradual change of MoO6 octahedra to MoO4 tetrahedra both being cross-linked with phosphate units without clustering. For WO3 glasses, minimum in DC conductivity is observed at 30–40 mol% of WO3 for temperatures from 303 to 513 K, followed by an increase in conductivity with further WO3 addition due to an increase in polaronic contribution. Observed turnover suggests a distinct transition from predominantly ionic to predominantly polaronic transport. On the contrary, for MoO3 glasses, conductivity decreases in the whole mixed compositional range indicating that the nature of transport is dominated by ionic component throughout the measured temperature range. A comparative study of Ag+, Li+, Na+ transport in MoO3/WO3 glasses reveals a strong correlation between pre-exponential factor and activation energy, which allows detection of the prevalence of conduction mechanism. Finally, the results demonstrate that Ag2O–WO3–ZnO–P2O5 glass system is a promising electrically tunable material with significant contributions of ionic or polaronic conductivity depending on composition.

CoxMg1-xFe2O4 (where x was 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) spinel ferrites were synthesized by the sol-gel combustion method using citric acid as fuel, following the rules of propellant chemistry. Amorphous powders were then calcined at 700 °C for 3 h. Structural analysis by X-Ray diffraction (XRD), FTIR and Raman spectroscopy confirmed the formation of a cubic spinel structure where the cation distribution and inversion degree depended on the Co2+ and Mg2+ ion content. Accordingly, the lattice parameter varied between 8.3703 A (MgFe2O4) and 8.3919 A (Co0.9Mg0.1Fe2O4) as did the crystallite size, from 34 nm (Co0.1Mg0.9Fe2O4) to 48 nm (Co0.9Mg0.1Fe2O4). Scanning electron microscopy (SEM) showed the formation of multigrain agglomerates. Determined values of the maximal and remanent magnetization, as well as coercive field, depended on the Co2+ and Mg2+ ion content and increased with substitution of diamagnetic Mg2+ ions with magnetic Co2+ ions. Most impressive is the increase of the coercive field from 74 Oe for MgFe2O4 to 1000 Oe for CoFe2O4, as well as an increase of magnetization in the field of 10 kOe from 27.4 emu g−1 to 75.7 emu g−1. The determined optical band gaps from UV/Vis DRS measurements showed a strong dependence on cation content, morphology, and crystallite size, decreasing from 2.09 eV for MgFe2O4 to 1.42 eV for CoFe2O4. The photocatalytic efficiency of as-synthesized ferrites was investigated by monitoring photocatalytic degradation of Methylene Blue (MB) under natural sunlight, and artificial light source emitting visible light. Different conditions of MB degradation such as photocatalyst loading, molar concentration of MB, and pH values were investigated. Results have shown that under both visible light and natural sunlight, excessive amounts of cobalt retarded the photocatalytic process. Co0.9Mg0.1Fe2O4 showed considerable activity (74.5% after 4 h) that is unexpected but possibly connected to structural anomalies. The best photocatalytic activity under natural sunlight was achieved by MgFe2O4 (82% after 4 h), while the best photocatalytic activity under visible light was achieved by Co0.1Mg0.9Fe2O4 (79% after 4 h).

A comprehensive study of selected properties of amorphous (a) Cu-TE alloys (TE=Ti, Zr and Hf) has been performed. Data for average atomic volumes of a- Cu-Hf, Ti alloys combined with literature data show that ideal solution behaviour (Vegard`s law) extends over the whole glass forming range (GFR) in all a-Cu-TE alloys. This enables one to obtain an insight into some properties and probable atomic arrangements for both, a-TEs (R. Ristić et. al., J. Alloys. Compd. 504S (2010) S194) and a-Cu by extrapolation of the data for alloys. Indeed the atomic volumes and other properties studied for all a-Cu-TE alloys extrapolate to the same values for a-Cu. Depending on the property, these values are either close to those of crystalline (c) Cu, or are close to those for liquid (L) Cu. In particular, the electronic transport properties of a-Cu seem close to those of L-Cu, whereas the static properties, such as the density of states, Young`s modulus, etc., converge to those of c-Cu. The possible impact of these results on our understanding of a-Cu-TE alloys, including glass forming ability, is discussed.

We have measured the magnetization and ac susceptibility of Hf 100− x Fe x (20 ≤ x ≤ 90) metallic glasses in the temperature range 1.5–300 K and magnetic fields up to 5.5 T. For 25 ≤ x ≤ 43 the magnetic susceptibility increases rapidly with x due to the onset of magnetic correlations in the vicinity of the transition into the ferromagnetic state, x c ∼50. However, for 35 ≤ x ≤ 43 the alloys consist of self-assembled magnetic nanoclusters embedded within a paramagnetic matrix. These clusters grow rapidly with increasing x . Thus, Hf–Fe glassy alloys evolve from the superconducting through superparamagnetic to ferromagnetic state with increasing Fe-content. The results are compared with those for Zr–Fe glassy alloys.

A recent study of Cu 55 Hf 45 − x Ti x metallic glasses with 0 ≤ x ≤ 45 has revealed the formation of bulk metallic glasses (BMG) for 15 ≤ x ≤ 30 . In the same composition range, the ratio of the glass transition temperature T g , and the liquidus temperature T l , showed a shallow maximum, consistent with the highest glass forming ability (GFA). Here, we present the results for some mechanical properties (Young’s modulus and microhardness) and magnetic properties (magnetic susceptibility) of these alloys and compare their variation with x with those for T g and the crystallization temperature T x . All measured properties show monotonic variations with x with no particular features in the composition range for BMG formation, hence do not indicate BMG compositions. The applicability of different criteria for assessing GFA to studied alloy system is briefly discussed.

Wide glass-forming ranges in TE-TL alloys (TE = Ti, Zr and Hf ; TL = Co, Ni and Cu) combined with often linear variation of their properties with composition makes it possible to predict the physical properties of the alloys which have not been prepared as yet (including pure amorphous TE). Recently, we explored this possibility for paramagnetic amorphous Zr-TL alloys in order to obtain parameters associated with the electronic structure and interatomic bonding of amorphous Zr. The comparison of these parameters with the results of the electronic structure calculations for different crystalline phases of Zr indicated an fcc-like local atomic structure for amorphous Zr. Here we provide new data for magnetic susceptibility () , superconducting transition temperature (Tc) and Young, s modulus (E) extending over a wide composition range of amorphous Hf-TL and Ti-TL alloys. We combine our results with published data in order to obtain a set of parameters appropriate to hypothetical amorphous Hf and Ti. As in the case of amorphous Zr these parameters are very different from those of stable crystalline phases (hcp) of Hf and Ti and indicate, as for Zr, an fcc-like short range order for amorphous Hf and Ti, too. This results in an enhanced electronic density of states at the Fermi level, N(EF) and thus in enhanced  and Tc, but in weakened interatomic bonding (low values of E and the Debye temperatures, D).

Magnetic properties of single crystals of the heterometallic complex [Cu(bpy)$_3$]$_2$[Cr(C$_2$O$_4$)$_3$]NO$_3\cdot $9H$_2$O (bpy = 2,2'-bipyridine) have been investigated. From the recorded EPR spectra, the spin-Hamiltonian parameters have been determined. The magnetization measurements have shown magnetic anisotropy at low temperatures, which has been analysed as a result of the zero-field splitting of the Cr$^{\mathrm{III}}$ ion. By fitting the exactly derived magnetization expression to the measured magnetization data, the axial zero-field splitting parameter, D, has been calculated. Comparing to the EPR measurements, it has been confirmed that $D$ can be determined from the measurements of the macroscopic magnetization on the single crystals.

Nanocrystalline Al-doped nickel ferrite powders have been synthesized by sol-gel auto-ignition method and the effect of non-magnetic aluminum content on the structural and magnetic properties has been studied. The X-ray diffraction (XRD) revealed that the powders obtained are single phase with inverse spinel structure. The calculated grain sizes from XRD data have been verified using transmission electron microscopy (TEM). TEM photographs show that the powders consist of nanometer-sized grains. It was observed that the characteristic grain size decreases from 29 to 6 nm as the non-magnetic Al content increases, which was attributed to the influence of non-magnetic Al concentration on the grain size. Magnetic hysteresis loops were measured at room temperature with a maximum applied magnetic field of 1T. As aluminum content increases, the measured magnetic hysteresis curves become more and more narrow and the saturation magnetization and remanent magnetization both decreased. The reduction of agnetization compared to bulk is a consequence of spin non-collinearity. Further reduction of magnetization with increase of aluminum content is caused by non-magnetic Al^{3+} ions and weakened interaction between sublattices. This, as well as the decrease in hysteresis was understood in terms of the decrease in particle size., 24 pages, 6 figures

A new magnetic transition in the ruthenocuprate parent compound RuSr2EuCeCu2O10 has been observed below 10 K. It shows up only as a kink in the imaginary part of the ac susceptibility and exhibits a pronounced frequency dependence. At the same time, the real part of the ac susceptibility and the dc magnetization study show very little change in the same temperature window suggesting only a minor fraction of the material to be involved in the transition. Frequency dependence shows excellent agreement with the predictions of the Arrhenius law known to describe well the dynamics of the superparamagnetic particles. The same type of the investigation on the RuSr2Eu1.1Ce0.9Cu2O10 composition showed no evidence of the similar transition, which points to a possible intrinsic behavior., Comment: to be published in Physica C

Two novel compounds of the formulae [{Cu(phen) 2 } 2 (μ-C 2 O 4 )][Cu(phen) 2 (μ-C 2 O 4 )NbO(C 2 O 4 ) 2 ] 2 · 8H 2 O ( 1 ) and [{Cu(bpy) 2 } 2 (μ-C 2 O 4 )][Cu(bpy) 2 (μ-C 2 O 4 )NbO(C 2 O 4 ) 2 ] 2 · 0.5bpy · 7H 2 O ( 2 ) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been prepared and characterized by single crystal X-ray diffraction, IR spectroscopy and magnetic susceptibility measurements. The molecular structure of both 1 and 2 consists of a discrete Cu II Cu II oxalate-bridged dinuclear [{Cu(L) 2 } 2 (μ-C 2 O 4 )] 2+ cation ( A unit) and two Cu II Nb V oxalate-bridged dinuclear [Cu(L) 2 (μ-C 2 O 4 )NbO(C 2 O 4 ) 2 ] − anions ( B units) (L = phen, bpy). In 1 a crystallographic inversion centre is located in the middle of the oxalate bridge of the A unit, whereas in 2 an analogous inversion centre is missing. In the A units the copper(II) atoms adopt a tetragonally elongated octahedral coordination with the equatorial planes being perpendicular to the mean planes of the oxalate bridge and parallel to each other. In both structures, similar one-dimensional motifs are generated through the ligand stacking interactions, with a difference that one free bipyridine molecule, present in 2 , intercalates into one of the motifs. It is shown that the phenanthroline ligand, due to its ability of stacking through the central aromatic ring, causes longer intermolecular Cu⋯Cu distances than the bipyridine ligand. The magnetic susceptibility measurements (1.8–290 K) show the ferromagnetic exchange interaction between the copper(II) atoms in the A units of both compounds, with J = +5.9 cm −1 and +7.9 cm −1 for 1 and 2 , respectively ( J – the exchange parameter in the isotropic spin Hamiltonian H INT = − J S 1 · S 2 ).

New families of mononuclear and heteropolynuclear complexes have been obtained by using [Cu(AA)(BB)]+ building-blocks (AA=acetylacetonate or salicylaldehydate; BB=1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine). The following mononuclear complexes have been structurally characterized: [Cu(acac)(Me2bipy)]ClO4 (1), [Cu(acac)(Me2bipy)(NCS)] (2), [Cu(acac)(phen)(NCS)] (3). In compound 1 the copper(II) exhibits a square planar geometry, while the stereochemistry of compounds 2 and 3 is square pyramidal, with the isothiocyanato ligand coordinated in the apical position. The reaction between 2 and HgCl2 affords a trinuclear complex, [{Cu(acac)(Me2bipy)(μ-NCS)}2Hg(SCN)2] (4). The reaction between 3 and HgCl2 leads to tetranuclear Cu2Hg2 compound, [{Cu(acac)(phen)(NCS)}2{(ClHg)2(NCS)2}] (5), with a unique structure, and to a trinuclear complex, [{Cu(acac)(phen)(NCS)}2Hg(SCN)2] (6). The structure of 5 consists of a {Hg2(NCS)2} ring on which two [Cu(acac)(phen)(NCS)] moieties are attached. In compounds 4, 5 and 6 the mercury atoms are tetracoordinated. By reacting [Cu(sal)(phen)(OClO3)] with (NEt4)2[Co(NCS)4], a heterohexanuclear compound is obtained: [{Cu(sal)(phen)(SCN)}2Co(NCS)2]2 (7), with the following topology of the metallic centers: Cu–Co–Cu–Cu–Co–Cu. The cobalt(II) ions in 7 are tetracoordinated by nitrogen atoms arising from two bridging and two terminal thiocyanato ligands. The central copper(II) ions are bridged by the phenoxo oxygen atom arising from the sal− ligand. The cryomagnetic properties of compounds 2–5 and 7 have been investigated and discussed. The magnetic behavior of compounds 2–5 has been ascribed to intermolecular exchange interactions mediated by the stacking interactions. The magnetic interaction between Cu(II) and Co(II) in 7 was found ferromagnetic (J=+0.6 cm−1), as theoretically predicted. The exchange interactions between the central copper(II) ions is antiferromagnetic (J=−5.8 cm−1).

The scope of this article is to report very detailed results of the measurements of magnetic relaxation phenomena in the new Cu$_{0.5}$Fe$_{2.5}$O$_{4}$ nanoparticles and known CuFe$_{2}$O$_{4}$ nanoparticles. The size of synthesized particles is (6.5$\pm $1.5)nm. Both samples show the superparamagnetic behaviour, with the well-defined phenomena of blocking of magnetic moment. This includes the splitting of zero-field-cooled and field-cooled magnetic moment curves, dynamical hysteresis, slow quasi-logarithmic relaxation of magnetic moment below blocking temperature. The scaling of the magnetic moment relaxation data at different temperatures confirms the applicability of the simple thermal relaxation model. The two copper-ferrites with similar structures show significantly different magnetic anisotropy density and other magnetic properties. Investigated systems exhibit the consistency of all obtained results., 18 pages, 8 figures

We report measurements of thermal conductivity in 30-350K range of hard fullerene-based carbon. The material has been prepared from C60 fullerene under pressure of 2.6-3 GPa and a temperature of 427K 1 and has an unusual combination of big hardness and high electrical conductivity which maybe related to complex bonding2. Its thermal conductivity is about 12W ImK at a room temeperature and decreases almost linearly as temperature decreases. The data obtained bear resemblance to the thermal properties of diamondlike and glassy carbon3 what allows to suggest existence of short range crystalline order in this transformed substance.