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The contribution of clusters of different sizes to magnetism and the switching of electron scattering mechanisms in amorphous Fe67Cr18B15 alloy during ion Ar+ irradiation is studied. The cluster magnetism is found to be related to the presence of clusters of the following two types: large α-(Fe, Cr) clusters of size D = 150–250 A and small (D = 40–80 A) clusters in a random intercluster medium. The generation of small ferromagnetic and antiferromagnetic clusters during ion irradiation leads to the formation of cluster glass, which affects the electrical properties of the alloy and causes a magnetic frustration. The temperature dependence of the barrier height is shown to characterize the magnetic state of the alloy in low fields. On the whole, the temperature dependence of the order parameter is a universal characteristic of the system. The temperature dependence of resistivity of initial alloys in the temperature range 98–300 K (ρ(T) ∝ T2) is determined by electron scattering by quantum defects, and the transition into a ferromagnetic state is revealed when the derivative ∂ρ/∂T ∝ T is analyzed. The increase in resistivity and the relation ρ ∝ T1/2 in strongly inhomogeneous samples after irradiation at a dose Φ = 1.5 × 1018 ions/cm2 are caused by weak localization effects, and the transition to a ferromagnetic state becomes obvious when the derivative ∂ρ/∂T ∝ T–1/2 is considered. Irradiation by fluence Φ = 3 × 1018 ions/cm2 induces a giant (twofold) increase in the alloy density, restores the ferromagnetism of large clusters, decreases the resistivity by 37%, and restores the relation ρ(T) ∝ T2, which results from the overlapping of the irradiation-induced small clusters when their concentration increases and from an increase in the alloy density. The overlapping of clusters lowers the barrier height and decreases the sensitivity of the alloy to an applied field. The relation ρ(T) ∝ T2 is valid for the entire temperature range T = 2–300 K because of the partial screening of the magnetic moments of large clusters by a medium having the properties of cluster glass.

The magnetocaloric effect in the vicinity of the martensitic transformation for a single crystalline alloy with a composition close to the stoichiometric Ni2MnGa has been determined indirectly by M(T,H) magnetization measurements. It has an inverse character. The magnetocaloric parameters, i.e., the magnetic entropy change, refrigeration capacity and various hysteretic effects have been calculated from the M(T,H) dependences. Besides the martensitic transition a weak entirely separated intermartensitic transition was observed. These two successive magneto-structural transformations give contributions to the observed magnetocaloric effect. Unusual dependence of entropy change as a function of magnetic field has been explained as arising because of two different mechanisms. Additionally, to confirm that studied martensitic transformation is a first order phase transition electrical resistivity and thermoelectric power measurements have been performed.

Clinical Scenario: Lower-extremity injuries in the United States costs millions of dollars each year. Athletes should be screened for neuromuscular deficits and trained to correct them. The tuck jump assessment (TJA) is a plyometric tool that can be used with athletes. Clinical Question: Does the TJA demonstrate both interrater and intrarater reliability in healthy individuals? Summary of Key Findings: Four of the 5 articles included in this critically appraised topic showed good to excellent reliability; however, caution should be taken in interpreting these results. Although composite scores of the TJA were found to be reliable, individual flaws do not demonstrate reliability on their own, with the exception of knee valgus at landing. Aspects of the TJA itself, including rater training, scoring system, playback speed, volume, and number of views allotted, need to be standardized before the reliability of this clinical assessment can be further researched. Clinical Bottom Line: The TJA has shown varying levels of reliability, from poor to excellent, for both interrater and intrarater reliability, given current research. Strength of Recommendation: According to the Centre for Evidence Based Medicine levels of evidence, there is level 2b evidence for research into the reliability of the TJA. This evidence has been demonstrated in elite, adolescent, and college-level athletics in the United Kingdom, Spain, and the United States. The recommendation of level 2b was chosen because these studies utilized cohort design for interrater and intrarater reliability across populations. An overall grade of B was recommended because there were consistent level 2 studies.

We present studies of the influence of the chemical composition changes on the type of magnetic order present in bulk nanocomposite Ge 1− x−y Pb x Cr y Te crystals with the average Pb-content close to x ≈ 0.20 and Cr-content, y , varying from y = 0.017 up to 0.043. Detailed magnetometric studies revealed the existence of two ordered magnetic states present in all our samples. All our crystals show a paramagnet to spin-glass-like state transition at temperatures from 135 K to 145 K, related to the presence of Cr 5 Te 8 clusters in the host lattice. The second transition type depends on the Cr-content, y . In the case of samples with y equal to 0.038 and 0.043 the ferromagnetic phase is observed with T C slightly below 70 K, while in samples with lower chromium concentration the presence of spin-glass-like state slightly below 50 K is observed. The presence of clusters in our samples has significant impact on the carrier transport and magnetotransport in our samples. The presence of critical scattering on the magnetic impurities is observed in resistivity and magnetoresistance data. Nearly-linear magnetoresistance is also observed in our samples indicating a presence of strong scattering on the grain boundaries in our samples.

We show that сluster magnetism in ferromagnetic amorphous Fe 67 Cr 18 B 15 alloy is related to the presence of large, D =150–250 A, α- ( Fe Cr ) clusters responsible for basic changes in cluster magnetism, small, D =30–100 A, α -( Fe, Cr ) and Fe 3 B clusters and subcluster atomic α -( Fe, Cr, B ) groupings, D =10–20 A, in disordered intercluster medium. For initial sample and irradiated one ( Φ =1.5×10 18 ions/cm 2 ) superconductivity exists in the cluster shells of metallic α-(Fe, Cr ) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ =3×10 18 ions/cm 2 , the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ ( T )~ T 2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ =1.5×10 18 ions/cm 2 , the transition to a dependence ρ ( T )~ T 1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ =3×10 18 ions/cm 2 , a return to the dependence ρ ( T )~ T 2 is observed.

We present studies of magnetotransport properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition changing from 0.180 x y T SG around 90 K. The presence of strong anomalous Hall effect (AHE) with hysteresis is observed at T T SG . The data analysis allowed calculation of a correction to the Hall constant R H for T T SG and the AHE constant, R S . R S is around 10 −6 m 3 /C. R S and R H do not change strongly with temperature. The scaling law analysis has proved that the AHE in this system is due to the extrinsic mechanisms dominated by the skew scattering with relatively small contribution of the side jump process. Strong localization occurs in our system at T T SG and causes a presence of a minimum in the resistivity vs. temperature dependence. The magnetoresistance of our samples shows complex behavior at T T SG . The negative magnetoresistance is observed at T T nearly linear positive magnetoresistance is observed at temperatures from 20 K up to T ≈ T SG , where it reaches maximum. Positive linear magnetoresistance is related to the granular nature of our samples while the maximum near T SG is related to the giant spin-splitting of the valence band.

We present the studies of structural, electrical, and magnetic properties of bulk Sn 1 − x − y Cr x Eu y Te crystals with different chemical compositions varying in the range of 0.004 ≤ x ≤ 0.089 and 0.007 ≤ y ≤ 0.020. The structural characterization of our samples indicated the clustering of the Cr-ions into Cr–Te related clusters. Eu ions do not form clusters and are randomly distributed in the SnTe lattice. The magnetotransport studies show the presence of positive linear magnetoresistance with maximum amplitude of about 80% for all our samples. Positive magnetoresistance is a geometrical effect related to the presence of clusters in the SnTe lattice. The cluster-glass-like state at the temperature of about 130 K is observed for x ≤ 0.025. The cluster-glass-like state is due to the presence of Cr-rich clusters in the SnTe lattice. The ferromagnetic behavior with the Curie temperature of about 275 K is observed for the samples with x > 0.077 indicating the presence of Cr 5 Te 8 clusters in the host material. Eu ions presence in our samples shows paramagnetic behavior.

This chapter presents the results of specific (photo)redox processes involving iron and manganese in surface seawaters. It attempts to assess the conjunctive effects of these processes in seawaters. The chapter presents and discusses the results of diurnal studies of iron and manganese speciation and partitioning between filterable and nonfilterable phases in a variety of marine systems. Thermodynamically, both iron (Fe) and manganese (Mn) are expected to predominate in oxidized form in seawater with iron present as Fe(III) oxyhydroxides and manganese present as Mn(III) and/or Mn(IV) oxides. The marine systems chosen for study are such that investigations are conducted on a unique water mass with mixing between water masses minimized as much as possible. Diurnal studies of the partitioning of manganese between 0.22-µm filtrand and filtrates indicate a strong dependency on light intensity. This is to be expected given the ability of light to retard both Mn(II) oxidation and to induce the reductive dissolution of Mn(III,IV) oxides.

We present studies of magnetic properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition varying in the range of 0.180 x y J pd , having values from 0.47 eV to 0.80 eV gives spin-glass transition temperature, T SG , values close to the experimental values for the Ge-rich phase. The magnetic order observed for the Pb-rich phase is also due to the carrier mediated magnetic interaction. The experimental transition temperatures are fitted with J pd value ranging from 0.22 eV to 0.28 eV.

A new tetranuclear [2 × 2] cluster of Cu(II) with a symmetric carbohydrazone based ligand, [Cu4L4](NO3)4·1.6(H2O) (1), {where HL donates bis-[(E)-N’-(1-(pyridin-2-yl)ethylidene)]carbohydrazide} was synthesized and characterized by spectroscopic methods and X-ray analysis. The EPR spectra were performed on single crystals of complex 1 at various temperatures and allowed the identification and separation of two types of magnetic objects contributing to magnetism: single atoms of Cu(II) and a tetranuclear Cu4 cluster. The main values of the g-factor and hyperfine structure were determined for single ions of Cu(II). The copper atoms in the tetramer are coupled antiferromagnetically with an isotropic antiferromagnetic exchange J = 215 K (149.4 cm−1). A small anisotropic exchange of the order of 0.06 K (0.04 cm−1) is responsible for the initial zero-field splitting of the energy levels in the tetramer spectrum. Magnetic measurements of complex 1 confirmed the existence of a strong antiferromagnetic exchange coupling between four Cu(II) ions. Complex 1 showed high potential for the catalytic and selective oxidation of cis-cyclooctene with aqueous H2O2.

L. Kilanski, M. Szyma«ski, B. Brodowska, M. Gorska, R. Szymczak, A. Podgorni, A. Avdonin, A. Reszka, B.J. Kowalski, V. Domukhovski , M. Arciszewska, W. Dobrowolski, V.E. Slynko and E.I. Slynko Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warszawa, Poland Faculty of Materials Engineering, Warsaw University of Technology, Woaoska 141, 02-507 Warszawa, Poland Institute of Materials Science Problems, Ukrainian Academy of Sciences, 5 Wilde Str., 274001 Chernovtsy, Ukraine

The Mn2−xFexP0.5As0.5 compounds (x = 0.7 and 1.0) studied exhibit the magnetic phase transitions, which are accompanied by a magnetic entropy change. For x = 1 the PM–FM transition is of the first order one with a weak (2–3 K) thermal hysteresis in the vicinity of TC = 275 K. The Mn1.3Fe0.7P0.5As0.5 compound possesses two magnetic transitions: the second-order PM–FM transition at TC = 190 K, followed by the FM–AFM transition at TN = 90 K, leading to normal and inverse magnetocaloric effects, respectively. The maximum values of magnetic entropy change are equal to 17 J kg−1 K−1 in MnFeP0.5As0.5 and 5 J kg−1 K−1 in Mn1.3Fe0.7P0.5As0.5 for a field change of 5 T. The magnetic entropy changes were calculated using both the isofield magnetization curves versus temperature and the isothermal magnetization curves versus applied magnetic field. The magnetocaloric effect in MnFeAs0.5P0.5 is discussed in the terms of both the thermodynamic Maxwell relation and the Clausius–Clapeyron equation.

The electronic structure and magnetic properties of the kagome staircase compound Co3V2O8doped by 3-d elements (Mn, Mg and Zn) have been investigated using ab-initio FPLO method. We found that in the case of Mg and Zn the electronic densities of states near the Fermi energy is not significantly modified, however substitution the cobalt by manganese atom changed the band structure near the Fermi energy.

Currently, complex ferromagnetic semiconductor systems are of significant interest due to their potential applicability in spintronics. A key feature in order to use semiconductor materials in spintronics is the presence of room temperature ferromagnetism. This feature was recently observed and is intensively studied in several Mn-alloyed II-IV-V2 group diluted magnetic semiconductor systems. The paper reviews the origin of room temperature ferromagnetism in II-IV-V2 compounds. In view of our recent reports the room temperature ferromagnetism in Mn-alloyed chalcopyrite semiconductors with more than 5 molar % of Mn is due to the presence of MnAs clusters. The solubility of magnetic impurities in bulk II-IV-V2 materials is of the order of a few percent, depending on the alloy composition. High values of the conducting hole - Mn ion exchange constant Jpd have significant value equal to 0.75 eV for Zn0.997Mn0.003GeAs2. The sample quality has significant effect on the magnetotransport of the alloy. The magnetoresistance of the alloy change main physical mechanism from spin-disorder scattering and weak localization for homogeneous samples to cluster-related geometrical effect observed for nanocomposite samples. The magnetoresistance of the II-IV-V2 alloys can be then tuned up to a few hundreds of percent via changes of the chemical composition of the alloy as well as a degree of disorder present in a material. [Projekat Ministarstva nauke Republike Srbije, br. III45003]

We have been studying magnetic properties of magnetic ion clusters in ternary, quaternary, and quinary IV-VI and II-IV-V 2 diluted magnetic semiconductors with varying concentrations of different magnetic and non-magnetic cations. We observed clusters of different types, from non-random distribution of magnetic ions in the host lattice to precipitates with the crystalline structure different from that of the host. The size of such precipitates varied from 200 nm to 20 μm. Depending on the type and size of clusters we observed different magnetic properties of the compounds, such as paramagnetic, spin-glass, spin-glass-like, or ferromagnetic states. For example, Zn 1-x Mn x GeAs 2 compounds with x ≤ 0.053 were paramagnetic with evidence of small short-range magnetic interactions, while in the same material with x ≥ 0.078 we observed room-temperature ferromagnetism. In IV-VI DMS clusters usually created a spin-glass or spinglass- like state. However, in some Ge 1-x-y Pb x Mn y Te crystals we observed a co-existence of two very different spin-glasslike states with transition temperatures T 1 ≈ 5 K and T 2 ≈ 90 K.

Three new complexes of copper(II) with pseudohalide anions and ( E )- N ′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide (HL), namely azide bridged dinuclear [Cu(L)(μ-N 3 )] 2 ( 1 ), two-dimensional coordination polymer [Cu 2 (L) 2 (NCS) 2 ] n ( 2a ) and monomeric [Cu(L-H)(NCS) 2 ] ( 2b ), were synthesized. The complexes were characterized by elemental analyses and spectroscopic methods. The structures were unequivocally confirmed by X-ray diffraction, and further studied by means of EPR and magnetic susceptibility measurements. In all three complexes, the isonicotinohydrazide ligand coordinates to the copper center in the enolic form (–C N–N ). In complex 1 , the two bridging azide ligands connect the two metal centers in an end-on (EO) fashion, with the metal centers having an asymmetric square pyramidal geometry. Complex 2b is based on a square pyramid with the neutral isonicotinohydrazide ligand coordinating in a tridentate mode. By contrast, the Schiff base (L) − coordinates in a tetradentate ligand fashion in 2a as the oxygen atom of the amide unit in the enol form asymmetrically bridges two Cu centers and a third Cu center is coordinated through the pyridyl-N atom. The EPR spectrum of complex 2a , consisting of two poorly resolved resonance lines, points to the presence of a dynamical Jahn–Teller effect, typical for Cu 2+ ions in octahedral environments.

Two samples containing phases formed in the FeVO4-Co3V2O8 system were prepared by a conventional sintering method. The sample designated as H5 was one-phase with the howardevansite-type structure, while the sample designated as HL7 contained a mixture of H-type and lyonsite-type structures. The temperature dependence of the electron paramagnetic resonance (EPR) spectra and static magnetic susceptibility χ was investigated in the temperature range from liquid helium to room temperature. Both the EPR spectra and the dc magnetic susceptibility showed anomalous behavior indicating that the magnetic competition process may be responsible. A comparison of the obtained results with previous studies on related compounds with the same structure, i.e. M3Fe4V6O24 (M = Mg(II), Zn(II), and Cu(II)) revealed that the observed anomaly shifted to lower temperatures on replacing the non-magnetic ions by magnetic Co(II) ions. The temperature dependence of the inverse susceptibility χ−1 indicates the existence of antiferromagnetic interactions between Fe(III) and Co(II) spins in sample H5. The obtained values of the Curie-Weiss temperatures are lower than for the Mn3Fe4V6O24 compound and comparable to compounds from M3Fe4V6O24 systems with M diamagnetic cations. The introduction of cobalt cations intensifies the magnetic frustration what is reflected in the temperature dependence of the magnetic susceptibility at low temperatures.

The first mixed-metal azido bridged complex of Cr(III)–Na(I) has been prepared and its structure is determined. Reaction of chromium(III) chloride and sodium azide with bis-[(E)-N′-(1-(pyridin-2-yl)ethylidene)]carbohydrazide (HL) produced the tetranuclear complex [Cr2Na2(L)2(CH3OH)2(μ-N3)4(N3)2] (1) in good yield. The structure is composed of idealized octahedral [CrIII(N5O)] cores linked to the octahedral [Na(N4O2)] cores by two bridging azide ligands. Magnetic properties and EPR of 1 were also studied.

The magnetocaloric effect (MCE) in La1 − xSrxMnO3, Sm0.55Sr0.45MnO3, and PrBaMn2O6 compounds is studied. The maximum values of MCE (ΔTmax) determined by a direct method in the second and third compositions and in La0.9Sr0.1MnO3 are found to be much lower than those calculated from the change of the magnetic part of entropy in the Curie temperature (TC) and the Neel temperature (TN) range. The negative contribution of the antiferromagnetic (AFM) part of a sample in the La1 − xSrxMnO3 system at 0.1 ≤ x ≤ 0.3 decreases ΔTmax and changes the ΔT(T) curve shape, shifting its maximum 20–40 K above TC. Lower values of ΔTmax are detected in the range TC = 130−142 K in polycrystalline and single-crystal Sm0.55Sr0.45MnO3 samples cooled in air. If such samples were cooled in an oxygen atmosphere (which restores broken Mn-O-Mn bonds and, thus, increases the volume of CE-type AFM clusters), the maximum in the temperature dependence of MCE is located at TN (243 K) for CE-type AFM clusters. A magnetic field applied to a sample during the MCE measurements transforms these clusters into a ferromagnetic (FM) state, and both types of clusters decompose at T = TN. The PrBaMn2O6 composition undergoes an AFM-FM transition at 231 K, and the temperature dependence of its MCE has a sharp minimum at T = 234 K, where MCE is negative, and a broad maximum covering TC. The absolute values of MCE at both extrema are several times lower than those calculated from the change in the magnetic entropy. These phenomena are explained by the presence of a magnetically heterogeneous FM-AFM state in these manganites.

We have studied the relation between clusterization in the flux of a substance and the thickness of deposited films obtained by the magnetron and pulsed laser sputtering of La0.7Sr0.3MnO3 and YBa2Cu3O7 − δ targets, respectively. No cluster formation has been observed in the case of magnetron sputtering, which is explained by a low concentration of atoms (ions) in the sputtered material flux. In accordance with calculations for the flux of non-interacting atoms, the deposited film thickness (h) exhibits exponential decrease with increasing distance (L) from the target. In the case of pulsed laser sputtering, for which the concentration of sputtered substance in the plasma is four orders of magnitude higher, the h(L) curve sharply deviates from the calculated dependence for the distances L > 6.2 cm, which is explained by the onset of intense clusterization in the laser plasma flux.

The temperature dependence of dc magnetization and electron paramagnetic resonance (EPR) spectra of the β-Cu3Fe4V6O24 multicomponent vanadate were investigated. Dc magnetic measurements showed the presence of strong antiferromagnetic interactions (Curie-Weiss temperature, Θ ∼ 80 K) at high temperatures, while zero-field-cooled (ZFC) magnetization revealed a cusp-like maximum in low fields at Tf1 = 4.4 K, which coincides with the splitting of the ZFC and FC curves. Another maximum was registered at Tf2 = 3.0 K. These two temperatures (Tf1 and Tf2) could be regarded as freezing temperatures in the spin glass state of two magnetic sublattices of Fe1 and Fe2 ions. The EPR spectrum of β-Cu3Fe4V6O24 is dominated by a nearly symmetrical, very intense and broad resonance line centered at geff ∼ 2.0 that could be attributed to iron ions. Below 10 K, an additional EPR spectrum with g1 = 2.018(1) and g2 = 2.175(1) appears, as well as a very weak line at geff = 1.99(1). The former spectrum is probably is due to divalent copper ions, and the latter line due to vanadium V4+ complexes. The temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) was determined in the range of 3–300 K. Two low-temperature maxima in the temperature dependence of the integrated intensity (at 40 and 6 K) were fitted with a function suitable for pairs of exchange-coupled Fe3+ ions. A comparison of dc magnetic susceptibility and EPR integrated intensity indicates the presence of spin clusters, which play an important role in determining the low-temperature magnetic response of β-Cu3Fe4V6O24.

Based on Mn-doped chalcopyrites CdGeAs 2 , ZnGeAs 2 and ZnSiAs 2 the new dilute magnetic semiconductors with p-type conductivity were produced. Magnetization, electrical resistivity, magnetoresistance and Hall effect of mentioned compositions were studied. Their curves of temperature dependence of magnetization have the similar form in spite of complicated character, for which the concentration and mobility of the charge carriers are responsible. Thus, for T T >15 K for a frustrated ferromagnetics. In compounds with Zn these two states dilute by spinglass-like state. This specific feature is assigned to an attraction of Mn ions occupying neighboring sites and to the competition between the carrier-mediated exchange and superexchange interactions. Curie temperatures of these compounds are above room temperature. These are the highest Curie temperatures in the A II B IV C V 2 :Mn systems.

Iron and iron oxide nanoparticles in silica layers deposited by sol–gel techniques on Si wafers were formed and studied. It was shown that multifunctional nanoparticles of different iron oxides possessing various physical properties can be fabricated by means of post-growth annealing of (SiO2:Fe)/SiO2/Si samples in various atmospheres. The hematite, maghemite, and iron nanoparticles were found to be dominant upon annealing the samples in air, argon, and hydrogen atmosphere, respectively. The physical properties of produced hybrid structures were studied by Raman and FT-IR spectroscopy, spectroscopic ellipsometry, AFM, and magnetic measurements. The sol–gel technique with subsequent annealing procedure is demonstrated to be an effective method for the formation of multifunctional hybrid structures composed of iron or iron oxide nanoparticles in silica matrix.

We present a detailed study of layered semiconductor InSe doped with Mn. X- ray and neutron diffraction analyses of (In,Mn)Se single crystals show the presence of a main phase as solid solution, the second antiferromagnetic MnSe phase, and traces of In Se Mn In 1 x x − 4Se3. Magnetic measurements reveal ferromagnetic behavior of (In,Mn)Se with the Curie temperature about 800 K. The ferromagnetic cluster model and exchange interaction via 2D electron gas, as the reasons of spontaneous magnetization, are discussed. The dramatic transformation of (In,Mn)Se electron spin resonance (ESR) spectra as a function of temperature is revealed. At the magnetic field perpendicular to crystallographic c axis, a low-field line within the temperature range 70 down to 4.7 K is observed. It shifts to smaller magnetic fields with temperature decrease. Neutron diffraction studies reveal the strong rise for one of the reflection peaks with temperature decrease in the same temperature region where ESR spectra transformation occurs. This peak corresponds to double MnSe interplanar distance in the (111) direction what is a period of its magnetic lattice. Magnetic structure of (In,Mn)Se single crystal is discussed.

Temperature dependence of dc/ac magnetization and electron paramagnetic resonance (EPR) spectra of Pb2FeV3O11 iron lead vanadate has been investigated. The dc magnetic measurements have shown the presence of antiferromagnetic interactions with Curie–Weiss temperature, TCW = −15.2 K, in the high temperatures range while the field cooled (FC) magnetization revealed a maximum at TN = 2.5 K which coincides with a long range magnetic ordering. Temperature dependence of χ′ has shown a maximum at the same temperature. EPR spectrum of Pb2FeV3O11 at room temperature is dominated by nearly symmetrical, very intense and broad resonance line centered at geff ∼ 2.0 that could be attributed to the correlated system of iron ions. The temperature dependence of magnetic resonance parameters (amplitude, g-factor, linewidth, integrated intensity) has been determined in the 4–300 K range and it suggests the existence of short range correlated spin system up to high temperatures. The temperature dependence of the amplitude of the resonance line has shown a pronounced maximum at 12.5 K that indicates on the existence of two subsystems of weakly and strongly coupled iron pairs. Comparison of dc magnetic susceptibility and EPR integrated intensity points to the presence of correlated spin agglomerates that play an important role in determination of the magnetic response of Pb2FeV3O11.

The effect of equal-channel multi-angle pressing combined with hydroextrusion and drawing followed by thermal treatment on critical current density, superconducting transition temperature and mechanical properties of a multi-fibre (210 fibres) superconducting wire made of a Nb + 50 wt% Ti alloy has been investigated.

Based on the Mn-doped chalcopyrites CdGeAs2, ZnGeAs2 and ZnSiAs2, new dilute magnetic semiconductors with the p-type conductivity were produced. Magnetization, electrical resistivity and Hall effect of these compositions were studied. Their temperature dependences of magnetization are similar in form in spite of a complicated character, which is controlled by the concentration and mobility of the charge carriers. Thus, for T < 15 K, these curves are characteristic of superparamagnets and for T > 15 K, of a frustrated ferromagnet. In compounds with Zn these two states are diluted by a spinglass-like state. This specific feature is ascribed to attraction of Mn ions occupying neighboring sites and to competition between the carrier-mediated exchange and superexchange interactions. The Curie temperatures of these compounds are above room temperature. These are the highest Curie temperatures in the AIIBIVCV2:Mn systems.

The effect of equal-channel, multiple-angle pressing combined with hydroextrusion and drawing, on the critical current density, pinning force, and superconducting transition temperature of bimetallic Nb+60at.% Ti wires is examined.

The heterostructure ferromagnetic/semiconductor ZnSiAs2/Si was obtained by using the Si-ZnAs2 phase diagram. The magnetic properties of Zn1-XMnXSiAs2 bulk crystals and ferromagnetic layered heterostructures were similar. The same method was used for preparing a ferromagnetic layer ZnGeAs2 on a germanium substrate.

Magnetic and electron paramagnetic resonance (EPR) properties of EuFe3(BO3)4 single crystals have been studied over the temperature range of 300–4.2 K and in a magnetic field up to 5 T. The temperature, field and orientation dependences of susceptibility, magnetization and EPR spectra are presented. An antiferromagnetic ordering of the Fe subsystem occurs at about 37 K. The easy direction of magnetization perpendicular to the c axis is determined by magnetic measurements. Below 10 K, we observe an increase of susceptibility connected with the polarization of the Eu sublattice by an effective exchange field of the ordered Fe magnetic subsystem. In a magnetic field perpendicular to the c axis, we have observed an increase of magnetization at T < 10 K in the applied magnetic field, which can be attributed to the appearance of the magnetic moment induced by the magnetic field applied in the basal plane. According to EPR measurements, the distance between the maximum and minimum of derivative of absorption line of the Lorentz type is equal to 319 Gs. The anisotropy of g-factor and linewidth is due to the influence of crystalline field of trigonal symmetry. The peculiarities of temperature dependence of both intensity and linewidth are caused by the influence of excited states of europium ion (Eu3+). It is supposed that the difference between the g-factors from EPR and the magnetic measurements is caused by exchange interaction between rare earth and Fe subsystems via anomalous Zeeman effect.

New diluted magnetic semiconductors (CdGeAs2:Mn, ZnGeAs2: Mn, and ZnSiAs2: Mn chalcopyrites) were synthesized. Magnetization M, electrical resistivity, magnetoresistance, and the Hall effect of these compositions were examined. Although the M(T) curves are complicated, they are similar in shape, for which the concentration and mobility of the charge bearers. Their Curie points are higher than 300 K, the highest in systems of the AIIBIVC2V: Mn type.

Optical and magnetooptical properties of opal photonic crystals modified by Co nanoparticles have been investigated by modulation spectroscopy technique in the visible spectral range from 400 to 800 nm. The Co nanoparticles of 1 to 8 nm in size were formed by means of chemical reduction reaction inside synthetic opal crystals composed of regularly close-packed SiO2 spheres of diameter 250–300 nm. As it was estimated from the spectral shift of the stop band of photonic crystals, Co nanoparticles occupied up to several percent of void volume in opal crystal lattice. In the Faraday configuration, external magnetic field induced the change in optical transmission normalized to sample thickness 1 cm and magnetic field 1 T equal to 0.10–0.35 for Co-modified opal crystals in the spectral range under consideration. The fabricated hybrid structures can be considered as a possible prototype of magnetophotonic crystals. Keywords: magnetophotonic crystals, modulation spectroscopy

Bi1 − xSrxFeO3 − x/2 (I), Bi1 − xSrxFe1 − xMnxO3 (II), and Bi1 − xCaxFe1 − xMnxO3 (III) solid solutions have been obtained. Their magnetization has been measured by X-ray and neutron diffraction and Mossbauer spectroscopy. According to the Mossbauer spectroscopy data, iron ions are in the trivalent state in system I. Near the concentration x ≈ 0.2, rhombohedral distortions (sp. gr. R3c) are transformed into tetragonal (P4/mmm). The symmetry of system II changes at x > 0.2 (R3c → R3c), whereas orthorhombic distortions (R3c → Pbnm) arise in system III at x > 0.2. The magnetic structure is antiferromagnetic (of G type). The samples of systems II and III exhibit weak ferromagnetism at x > 0.2 due to the Dzyaloshinski-Moriya interaction.

Using the results of magnetization measurements of LaSrMnO cluster glasses, it is shown that the concentration of frozen magnetic moments exponentially decreases with the increase of temperature. We find that temperature dependence of the order parameter q, of the form q − q ( T ) ∼ T − 5 / 2 , is universal characteristic of the investigated cluster glasses and that the barrier height Δ closely follows the quadratic relation to the temperature, Δ ≈ B T 2 .

A new p -type dilute magnetic semiconductor was synthesized on the basis of manganese-doped ZnSiAs 2 chalcopyrite. As the manganese percentage in ZnSiAs 2 increased, the Curie temperature increased from 325 to 337 K for compositions containing 1 and 2 wt % manganese. The ferromagnetic properties of the new dilute magnetic semiconductor were due to nanoclusters that were generated by concurrent substitution of manganese for elements in the cationic sublattice of chalcopyrite.

Magnetic interactions in a site-disordered multicomponent vanadate Mn3Fe4(VO4)6 are studied using DC magnetization and multifrequency Electron Paramagnetic Resonance (EPR). The static magnetic susceptibility χ shows antiferromagnetic interactions between Fe3+ and Mn2+ spins with a Curie–Weiss temperature Θ = −165(5) K. EPR measurements indicate a strong dependence of χ on the frequency and temperature. The EPR spectra due to iron and manganese ions are observed in the X-band. It is mostly manganese ions that are observed at 80 GHz while two kinds of magnetic centers are identified at frequencies above 160 GHz. The observed shifts of the resonance lines for Fe3+ ions at low frequencies differ from those at high frequencies. The observed features may be due to different magnetic sublattices which modify the magnetic ground state, while competing magnetic interactions may lead to magnetic frustration. It appears that the very high magnetic fields employed in our high-frequency EPR measurements may affect the spin-flop transitions anticipated below Neel temperature TN.

The magnetocaloric effect in La0.6Ca0.4MnO3 manganite has been investigated. The isothermal magnetization versus applied magnetic field at various temperatures in the vicinity of Curie temperature was measured, and the temperature dependence of magnetic entropy change was determined using Maxwell’s relation. This value is comparable to that in Gd. Nevertheless, the relative cooling power of La0.6Ca0.4MnO3 was shown to be considerably lower than that of Gd. The experimental results have been analyzed in frames of a phenomenological statistical model. This model considers explicitly Jahn-Teller interactions and allows prediction of the field dependences of the magnetic entropy change and the relative cooling power.

Based on Mn-doped chalcopyrite ZnSiAs2 the new dilute magnetic semiconductor with p-type conductivity was produced. The Curie temperature behavior of the produced semiconductor is distinctly dependent on the Mn concentration: 325 K for 1 wt.% and 337 K for 2 wt.% of Mn, consequently. Magnetization, electrical resistance, magnetic resistance and Hall effect of mentioned compositions were studied. Temperature dependence of magnetization M(T) have complicate behavior. For T  15 K the M(T) dependence is characteristic for superparamagnetic and at T > 15 K magnetization is sum of magnetizations of ensemble of superparamagnetic clusters and ferromagnetic phase contained frustration regions.

Anomalies of a variable range hopping (VRH) in amorphous LaSrMnO films containing ferromagnetic (FM) and antiferromagnetic (AFM) crystalline clusters are investigated. Anomalies are constituted, in the 190–130 K temperature interval, by an increase of the local activation energy ( e a ) with decreasing temperature. It is established that the increase in e a is caused by magnetic ordering of AFM clusters containing Mn 3+ and Mn 4+ centers participating in VRH.

A new spintronics material with the Curie temperature above room temperature, the ZnSiAs2 chalcopyrite doped with 1 and 2 wt % Mn, is synthesized. The magnetization, electrical resistivity, magnetoresistance, and the Hall effect of these compositions are studied. The temperature dependence of the electrical resistivity follows a semiconducting pattern with an activation energy of 0.12–0.38 eV (in the temperature range 124 K ≤ T ≤ 263 K for both compositions). The hole mobility and concentration are 1.33, 2.13 cm2/V s and 2.2 × 1016, 8 × 1016 cm−3 at T = 293 K for the 1 and 2 wt % Mn compositions, respectively. The magnetoresistance of both compositions, including the region of the Curie point, does not exceed 0.4%. The temperature dependence of the magnetization M(T) of both compositions exhibits a complicated character; indeed, for T ≤ 15 K, it is characteristic of superparamagnets, while for T > 15 K, spontaneous magnetization appears which correspond to a decreased magnetic moment per formula unit as compared to that which would be observed upon complete ferromagnetic ordering of Mn2+ spins or antiferromagnetic ordering of spins of the Mn2+ and Mn3+ ions. Thus, for T > 15 K, it is a frustrated ferro- or ferrimagnet. It is found that, unlike the conventional superparamagnets, the cluster moment μc in these compositions depends on the magnetic field: ∼12000–20000μB for H = 0.1 kOe, ∼52–55μB for H = 11 kOe, and ∼8.6–11.0μB at H = 50 kOe for the compositions with 1 and 2 wt % Mn, respectively. The specific features of the magnetic properties are explained by the competition between the carrier-mediated exchange and superexchange interactions.

Fluxes with a wide stability range of trigonal DyFe3(BO3)4 were selected by the successive-approximation method using direct phase probing in the Bi2Mo3O12-B2O3-Dy2O3-Fe2O3 system. Crystallization parameters of the fluxes were determined. The conditions for single-crystal growth were recommended using both spontaneous crystal nucleation and seeded growth according to the Kyropoulos method. An analysis of the measured temperature and field dependences of magnetization of crystals in fields parallel or perpendicular to the threefold axis led to the conclusion that DyFe3(BO3)4 undergoes a phase transition to an ordered easy-axis state and is characterized by a field-induced spin-reorientation transition with the predominant alignment of Dy3+ spins along the applied field.

Sediment metal concentrations in embayments of Sydney Harbour, acquired from the literature and from samples collected for this study, were used to generate contaminant probability density distributions using AQUARISK. The sediment metal concentrations often exceeded Australia's interim sediment quality guidelines. Similarly, estuarine spiked sediment toxicity test literature provided adverse biotic effects concentration data to generate species sensitivity distributions using AQUARISK. Although the harbor is subject to other inorganic and organic contamination, we have used sediment metals to demonstrate an approach for ecological risk mapping and environmental management prioritization. Sufficient spiked sediment toxicity test data were found for only three metals—Cd, Cu, and Zn—and some tests were likely to overestimate toxicity. The estimates of the hazardous concentration to 5% of species (the 50th percentile of the 95% species protection level) were 5, 12, and 40 mg/kg DW of total sediment ...

We performed implantation experiments; applying both the chemically active oxygen ions and inactive ions of neon noble gas, to thin epitaxial films of (Ga,Mn)As ferromagnetic semiconductor. Inspection of their magnetic properties by means of a superconducting quantum interference device magnetometer revealed that the implantation with a low dose of either O or Ne ions completely suppressed ferromagnetism in the films. Both the high resolution X-ray diffraction technique and the Raman spectroscopy showed significant changes in the structural and optical properties of the films caused by oxygen and neon implantation.