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The temperature dependence of the thermal conductivity k(T) of the AsxS100-x glass system was studied down to 1.8 K in a wide range of various (x = 20, 28.6, 40, 45, and 50) compositions. Universal glass anomalies in k(T) were revealed. The temperature dependence k(T) ∼ T2 onset at the lowest temperatures and plateau below 15 K were detected. The plateau formation is sample quality sensitive and composition-dependent. It was experimentally found that even with a slow cooling rate, several samples were cracked. Depending on the sample damage, the additional internal scattering process leads to the k(T) plateau suppression. The observed k(T) temperature dependence is similar to the glassy ceramics-like behavior. [ABSTRACT FROM AUTHOR]

The annealing behavior of (1-x)BiMg0.5Ti0.5O3–xBiZn0.5Ti0.5O3 [(1-x)BMT–xBZT] perovskite solid solutions synthesized under high pressure was studied in situ via X-ray diffraction and piezoresponse force microscopy. The as prepared ceramics show a morphotropic phase boundary (MPB) between the non-polar orthorhombic and ferroelectric tetragonal states at 75 mol. % BZT. It is shown that annealing above 573 K results in irreversible changes in the phase diagram. Namely, for compositions with 0.2 < x < 0.6, the initial orthorhombic phase transforms into a ferroelectric rhombohedral phase. The new MPB between the rhombohedral and tetragonal phases lies at a lower BZT content of 60 mol. %. The phase diagram of the BMT–BZT annealed ceramics is formally analogous to that of the commercial piezoelectric material lead zirconate titanate. This makes the BMT–BZT system promising for the development of environmentally friendly piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

An experimental study of the rotational magnetocaloric effect in Ni(en)(H2O)4SO4∙2H2O (en = ethylenediamine) single crystal is presented. The study was carried out at temperatures above 2 K and was associated with adiabatic crystal rotation between the easy plane and hard axis in magnetic fields up to 7 T. The magnetocaloric properties of the studied system were investigated by isothermal magnetization measurement. The experimental observations were completed with ab initio calculations of the anisotropy parameters. A large rotational magnetic entropy change ≈12 Jkg−1K−1 and ≈16.9 Jkg−1K−1 was achieved in 5 T and 7 T, respectively. The present study suggests a possible application of this material in low-temperature refrigeration since the adiabatic rotation of the single crystal in 7 T led to a cooldown of the sample from the initial temperature of 4.2 K down to 0.34 K. Finally, theoretical calculations show that S = 1 Ni(II)-based systems with easy-plane anisotropy can have better rotational magnetocaloric properties than costly materials containing rare-earth elements in their chemical structures. [ABSTRACT FROM AUTHOR]

The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1-y)BiFeO3-yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1-y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1-y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1-yB3+ yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed. [ABSTRACT FROM AUTHOR]

Precipitation of nanocrystallites of cobalt–aluminium layered double hydroxides in a magnetic field has been studied. In a magnetic field perpendicular to the substrate, dense and homogeneous films have been obtained. Magnetic anisotropy of the crystallites is explained by deviation from the statistical cation distribution in favour of honeycomb-like coordination of cobalt. [ABSTRACT FROM AUTHOR]

Comparative analysis of experimentally measured Raman spectra of crystalline (c), glassy (g), and powdered c‐As2S3 samples is performed based on vibrational modes of As6S6+6/2 ring‐like nanoclusters being fully ("rigid") or partially ("soft") interconnected with the glassy matrix, calculated using density functional theory (DFT). Although good agreement is found in the 100–500 cm−1 spectral range, the DFT simulations show additional super‐low frequency modes of "soft" rings at wavenumbers being significantly lower than the "rigid" ring's vibrational band at 26 cm−1. Broadening of the relatively narrow low‐frequency band of "rigid" clusters is found to be dependent on the number of interconnections of "soft" clusters with the glassy matrix, demonstrating mixing of "rigid" and "soft" vibrations in the boson peak region of g‐As2S3. In addition, the shift of the super‐low frequency Raman modes of "soft" nanoclusters and equivalent characteristic temperature are found to be nonlinearly dependent on the number of interconnections. Comparison with experimental Raman spectroscopic and heat capacity data indicates that the main contribution of both the LF Raman intensity and the low‐temperature anomaly of specific heat at 5.3 K comes from "soft" clusters with four and two interconnections. [ABSTRACT FROM AUTHOR]

Exchange bias (EB) phenomena have been observed in Nd2/3Ca1/3MnO3 colossal magnetoresistance perovskite below the Curie temperature TC~70K and attributed to an antiferromagnetic-ferromagnetic (FM) spontaneous phase segregated state of this compound. Field cooled magnetic hysteresis loops exhibit shifts toward negative direction of the magnetic field axis. The values of exchange field HEB and coercivity HC are found to be strongly dependent of temperature and strength of the cooling magnetic field Hcool. These effects are attributed to evolution of the FM phase content and a size of FM clusters. A contribution to the total magnetization of the system due to the FM phase has been evaluated. The exchange bias effect decreases with increasing temperature up to TC and vanishes above this temperature with disappearance of FM phase. Relaxation of a non-equilibrium magnetic state of the compound manifests itself through a training effect also observed while studying EB in Nd2/3Ca1/3MnO3. [ABSTRACT FROM AUTHOR]

A novel polymeric one-dimensional compound Cu(tn)Cl2 (tn = 1,3-diminopropane) is prepared and characterized. EPR, thermodynamic, and magnetic studies revealed a two-dimensional character of magnetic correlations with the intralayer J1lK(sub B) approximately equal to -3K and interlayer J' approximately equal to 10(super -3)J exchange coupling, where N-H...Cl hydrogen bonds mediate magnetic interactions.

We report the activation of platinum catalyst thin films for oxygen reduction reaction in perchloric acid electrolytes when the films are subjected to mechanical stress. The catalysts films were deposited by magnetron sputtering on photosensitive chalcogenide As20Se80 semiconductor glass layer. When platinum films are illuminated by red laser light the glass under semitransparent platinum film exhibits photo‐induced flow. The material flow underneath platinum film induces mechanical stress resulting in film wrinkling and significant increase in its catalytic activity. [ABSTRACT FROM AUTHOR]

We report a new antiferromagnetic radical‐anion salt (RAS) formed from 7,7,8,8‐tetracyanquinonedimethane (TCNQ) anion and 2‐amino‐5‐chloro‐pyridine cation with the composition of (N−CH3−2‐NH2−5Cl−Py)(TCNQ)(CH3CN). The crystallographic data indicates the formation of (TCNQ)2.− radical‐anion π‐dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π‐dimers characterize with strong π‐stacking "pancake" interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π‐dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ)2.− π‐dimers bound in the endless chainlets via supramolecular bonds with (N−CH3−2‐NH2−5‐Cl−Py)+ cations, the repulsion forces are screened, allowing for specific parallel π‐stacking interactions and stable radical‐anion dimers formation. Measurements of magnetic susceptibility and magnetization confirm antiferromagnetic properties of RAS, what is in line with the higher stability of ground singlet state of the radical‐anion pair, calculated by means of the DFT. Therefore, the reported radical‐anion (N−CH3−2‐NH2−5Cl−Py)(TCNQ)(CH3CN) solvate has promising applications in novel magnetics with supramolecular structures. [ABSTRACT FROM AUTHOR]

A post-synthesis thermal treatment of metastable phases in the high-pressure stabilised perovskite BiFe1−yScyO3 system results in the irreversible formation of polymorphs which represent novel polar and antipolar structures with interesting magnetic properties. Such annealing-stimulated polymorphism is believed to be a general phenomenon which can be found in other systems. [ABSTRACT FROM AUTHOR]

The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET)2[3,3′-Cr(1,2-C2B9H11)2] (ET = bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me4N)[3,3´-Cr(1,2-C2B9H11)2] in the galvanostatic regime. An electric conductivity σ (293 K) = 7 × 10−3 Ohm−1 cm−1 with semiconductor activation energy Ea ≅ 0.1 eV in the range of 127-300 K was observed. The crystal structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] was determined by X-ray diffraction at 173 K, revealing the presence of structural tetramers in radical-cation stacks. The magnetic properties of the complex were investigated in the temperature range 1.8-300 K using magnetometry and EPR, showing that the magnetic structure of (ET)2[3,3′-Cr(1,2-C2B9H11)2] consists of two independent magnetic subsystems. Cation radicals form a rectangular magnetic lattice in the ab-plane with significant antiferromagnetic exchange interactions. The chromium bis(dicarbollide) anions are characterized by unusually strong positive zero-field splitting of the Cr(III) ions, which was confirmed by ab initio calculations. [ABSTRACT FROM AUTHOR]

The agriculture sector is the principal source of income for around 20% of the EU-26 population, which live in predominantly rural regions that would be devastated without its contribution. Moreover, the combined agricultural and food sector forms an important part of the EU economy, accounting for 15 million jobs (8.3% of total employment) and 4.4% of GDP. The 12 million active farmers across Europe today, have an average farm size of about 15 ha, and are expected to meet the needs of 500 million Europeans. In addition, they are also expected to promote a sustainable and balanced development of their land, also in areas where production conditions are difficult. Yet, despite the relevance of the sector, the use of land for agriculture purposes is not very sustainable. Among other issues, there is a serious problem in respect of the abandonment of agricultural land. Based on the perceived need for research on this topic, the aim of this paper is to examine the causes and consequences of agricultural land abandonment, outlining its social, economic and environmental impacts, as well as the implications for territorial integration. [ABSTRACT FROM PUBLISHER]

Magnetic behavior of CoII(n)AlIII layered double hydroxides (LDHs) (n=Co/Al=2 and 3) intercalated with nitrate was studied as a function of temperature. Both LDH compounds are paramagnetic above about 8K. A rapid increase of their magnetic moments occurs below this temperature until the moments reach the maximum values at Tmax of 4.0K and 3.2K for Co(2)Al-NO3 and Co(3)Al-NO3, respectively. Below Tmax, the zero-field-cooled and the field-cooled static magnetization curves are strongly different. Along with this low-temperature phenomena, Co(2)Al-NO3 and Co(3)Al-NO3 demonstrate anomalous behavior of their temperature dependence magnetic susceptibility in a highertemperature range: between 75 and 175K, both the paramagnetic Curie temperature and the effective magnetic moment change in a non-monotonous way. Possible structural reasons of the observed magnetic behavior of the CoII(n)AlIII LDHs are discussed. [ABSTRACT FROM AUTHOR]

An increase of the spin-disorder resistivity with decreasing film thickness has been observed in thulium thin films prepared in UHV. X-ray diffraction investigation in thinner films with thickness below [approximately equal to] 100 nm revealed that this dependence is caused by a structural change.

The exchange bias (EB) phenomenon has been found in Nd2/3Ca1/3MnO3 perovskite. The phenomenon manifests itself as a negative horizontal shift of magnetization hysteresis loops. The EB phenomenon is evident of an interface exchange coupling between coexisting antiferromagnetic (AFM) and ferromagnetic (FM) phases and confirms the phase separated state of the compound at low temperatures. The EB effect is found to be strongly dependent on the cooling magnetic field and the temperature, which is associated with the evolution of spontaneous AFM-FM phase separated state of the compound. Analysis of magnetic hysteresis loops has shown that ferromagnetic moment M FM originating from the FM clusters saturates in a relatively low magnetic field about H ~ 0.4 T. The obtained saturation value MFM(1 T) ~ 0.45 µB is in a good agreement with our previous neutron diffraction data. [ABSTRACT FROM AUTHOR]

[Mn(L)(μ1,1-N3)2]2n[Mn(H20)2(μ1,1-N3)2]n (1) and [Cd(HL)(μ1,1-N3)2]n (2) have been synthe-sized from HL (HL: pyridine-2-carbaldehyde semicarbazone) and azide ligands, characterized by FT-IR, UV-vis spectroscopy and X-ray crystallography. Single crystal X-ray diffraction revealed that 1 is a coordination polymer consisting of two infinite 1-D chains: chain A with [Mn(L) (μ1,1-N3)2]2n and chain B with [Mn(H20)2(μ1,1-N3)2]n. In both chains, Mn centers are connected via two double end-on (EO) azide bridges. 2 is a coordination polymer consisting of a 1-D infinite chain, where Cd centers are connected via two double EO azide bridges. The electrochemistry of HL, 1 and 2 were studied by cyclic voltammetry. Magnetic susceptibility measurements indicate bulk ferromagnetic coupling for 1 below 5 K. Antimicrobial activities of both compounds 1 and 2 were greater than HL, with the strongest effect for 2 consistent with its larger radius and electronegativity of Cd(II) ions.[Mn(L)(n,i-N3)2]2„[Mn(H20)2(n1,-N3)2]„ (1) and [Cd(HLXnM-N3)2]„ (2) have been synthe-sized from HL (HL: pyridine-2-carbaldehyde semicarbazone) and azide ligands, characterized by FT-IR, UV-vis spectroscopy and X-ray crystallography. Single crystal X-ray diffraction revealed that 1 is a coordination polymer consisting of two infinite 1-D chains: chain A with [Mn(L) (Hi,i-N3)2]2„ and chain B with [Mn(H20)2(|i|,|-N3)2]„. In both chains, Mn centers are connected via two double end-on (EO) azide bridges. 2 is a coordination polymer consisting of a 1-D infinite chain, where Cd centers are connected via two double EO azide bridges. The electrochemistry of HL, 1 and 2 were studied by cyclic voltammetry. Magnetic susceptibility measurements indicate bulk ferromagnetic coupling for 1 below 5 K. Antimicrobial activities of both compounds 1 and 2 were greater than HL, with the strongest effect for 2 consistent with its larger radius and electronegativity of Cd(II) ions. [ABSTRACT FROM AUTHOR]

[Cu(bmen)2(H2O)2]F2∙4H2O (1) (bmen = N,N′-dimethylethane-1,2-diamine) and [Cu(bmen)2(BF4)2] (2) exhibit ionic and molecular crystal structures, respectively. In both1and2, Cu(II) exhibits tetragonally elongated six coordination in the 4 + 2 form with two chelatebmenin the equatorial plane; axial positions are occupied by weakly bound water in1while in2in these positions are fluorine from disordered BF4−. Packing in1and2are governed by hydrogen bonds (HBs). Magnetic studies from 1.8 to 300 K reveal that1and2follow the Curie–Weiss law with parametersθ = −0.88 K andg = 2.04 for1andθ = −0.58 K andg = 2.13 for2, suggesting the presence of weak antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

A giant exchange bias is detected in the colossal magnetoresistance of Nd2/3Ca1/3MnO3 perovskite at low temperatures and is evidence of intrinsic exchange coupling in this compound. These phenomena confirm our previous assumption that the low-temperature magnetic structure of this compound consists of small (nanosized) ferromagnetic clusters embedded in a charge-ordered antiferromagnetic matrix. The magnetic behavior of the perovskite Nd2/3Ca1/3MnO3 is consistent with a cluster-glass magnetic state and inconsistent with the classical spin-glass state observed in a variety of disordered magnetic systems. We think that the cluster-glass magnetic behavior of Nd2/3Ca1/3MnO3 originates in a self-organized phase-separated state of the compound. A Cole-Cole analysis of the dynamic susceptibility at low temperatures reveals an extremely broad distribution of relaxation times, indicating that spins are frozen on a 'macroscopic' time scale. Slow relaxation of the zero-field-cooled magnetization is also observed experimentally. This slow relaxation confirms the cluster-glass magnetic state of the compound. Two highly different relaxation mechanisms have been found: the first is characteristic of temperatures below the freezing temperature Tg ∼ 60 K and the second, of higher temperatures. [ABSTRACT FROM AUTHOR]

Magnetic properties of the high-pressure stabilized perovskite BiFe1-yScyO3 phases (0.1 ≤ y ≤ 0.9) have been studied by means of magnetization measurements and neutron diffraction. The metastable perovskites of this series undergo irreversible polymorphic transformations upon annealing, the phenomenon referred to as conversion polymorphism. It has been found that the solid solutions with y ≥ 0.70 exhibit no long-range magnetic ordering regardless of their polymorph modification, while those with y ≤ 0.60 are all antiferromagnets. Depending on the scandium content, temperature and structural distortions, three types of the antiferromagnetic orderings, involving collinear, canted and cycloidal spin arrangements, have been revealed in the phases obtained via conversion polymorphism and the corresponding magnetic phase diagram has been suggested. [ABSTRACT FROM AUTHOR]

The article presents the cover page and a brief information on the article related to turning catalysts on by light-induced stress.

Quantum Heisenberg chain and square lattices are important paradigms of a low-dimensional magnetism. Their ground states are determined by the strength of quantum fluctuations. Correspondingly, the ground state of a rectangular lattice interpolates between the spin liquid and the ordered collinear Néel state with the partially reduced order parameter. The diversity of additional exchange interactions offers variety of quantum models derived from the aforementioned paradigms. Besides the spatial anisotropy of the exchange coupling, controlling the lattice dimensionality and ground-state properties, the spin anisotropy (intrinsic or induced by the magnetic field) represents another important effect disturbing a rotational symmetry of the spin system. The S = 1/2 easy-axis and easy-plane XXZ models on the square lattice even for extremely weak spin anisotropies undergo Heisenberg-Ising and Heisenberg-XY crossovers, respectively, acting as precursors to the onset of the finite-temperature phase transitions within the two-dimensional Ising universality class (for the easy axis anisotropy) and a topological Berezinskii–Kosterlitz–Thouless phase transition (for the easy-plane anisotropy). Experimental realizations of the S = 1/2 two-dimensional XXZ models in bulk quantum magnets appeared only recently. Partial solutions of the problems associated with their experimental identifications are discussed and some possibilities of future investigations in quantum magnets on the square and rectangular lattice are outlined. [ABSTRACT FROM AUTHOR]

From the aqueous-methanolic systems Ni(NO 3 ) 2 – LiTCNQ – 5,5′- dmbpy and Ni(NO 3 ) 2 – LiTCNQ – 4,4′- dmbpy three novel complexes [Ni(5,5′ -dmbpy ) 3 ](TCNQ) 2 ( 1 ), [Ni(4,4′ -dmbpy ) 3 ](TCNQ) 2 ( 2 ) and [Ni(4,4′- dmbpy ) 3 ] 2 (TCNQ-TCNQ)(TCNQ) 2 ∙0.60H 2 O ( 3 ), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5′- dmbpy )] 2+ ( 1 ) or [Ni(4,4′- dmbpy )] 2+ ( 2 and 3 ). The anionic parts of the respective crystal structures 1 – 3 are formed by TCNQ ⋅- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ) 2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S  = 1 and TCNQ ⋅- anion-radicals with S  = 1/2 while the (TCNQ-TCNQ) 2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ ⋅- anion-radicals. [ABSTRACT FROM AUTHOR]

Organo-metallic compounds Cu( en )(H 2 O) 2 SO 4 ( en =C 2 H 8 N 2 ) and Cu( tn )Cl 2 ( tn =C 3 H 10 N 2 ) representing S =1/2 quasi-two-dimensional Heisenberg antiferromagnets with an effective intra-layer exchange coupling J/ k B ≈3 K, have been examined by specific heat measurements at temperatures down to nominally 50 mK and magnetic fields up to 14 T. A comparative analysis of magnetic specific heat in zero magnetic field revealed nearly identical contribution of short-range magnetic correlations and significant differences were observed at lowest temperatures. A phase transition to long-range order was observed in Cu( en )(H 2 O) 2 SO 4 at T C =0.9 K while hidden in Cu( tn )Cl 2 . A response of both compounds to the application of magnetic field has rather universal features characteristic for a field-induced Berezinskii–Kosterlitz–Thouless transition theoretically predicted for ideal two-dimensional magnets. [ABSTRACT FROM AUTHOR]

Iron–chromium nanoparticles (NPs) were obtained through the thermal decomposition of μ 3 -oxo heterotrinuclear {FeCr 2 O} acetate in the presence of sunflower oil and dodecylamine (DA) as surfactants. The average diameter of the NPs was 3.5 nm, as estimated on the basis of transmission electron microscopy and atomic force microscopy images. Both techniques revealed the formation of roughly approximated spheres with some irregularities and agglomerations in larger spherical assemblies of 50–100 nm. In hexane, NPs with diameters in the 2.33–4.85 nm range are individually dispersed, as emphasized by dynamic light scattering measurements. The amorphous nature of the product was emphasized by X-ray powder diffraction. The study of the magnetic properties shows the presence of superparamagnetic state of iron–chromium oxide NPs and the diamagnetic contribution from DA layer forming a shell of NPs. [ABSTRACT FROM AUTHOR]