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A large range of nanoscale superparamagnetic materials has been under scrutiny from the point of view of their potential theranostic, multimodal applications. In this paper we have investigated the effect of replacing Fe3+ cations with Gd3+ and Tb3+ in the core of the superparamagnetic iron oxide nanoparticles in search for the optimum level of magnetic core doping with these lanthanides. We have found that the presence of Gd3+ and Tb3+ up to 2.5% at. does not alter significantly the crystallographic structure of such nanoferrites and does not compromise the magnetic properties of doped nanoparticles. The doping level, though relatively small, exceeds the levels of currently used radiopharmaceuticals, where only few radionuclides can be incorporated in a single radiotherapeutic molecule. This new type of multifunctional nanoparticles can be used not only as drug carriers or in magnetic hyperthermia, but also in the so-called endoradiotherapy. The latter feature can be easily implemented upon the replacement of “cold” ions of Tb3+ and Gd3+ in the superparamagnetic core with their isotopes emitting soft β− radiation suitable for the internal radiotherapy, localized directly within the tumor. Therefore, these nanoparticles can be used simultaneously in targeted drug delivery, hyperthermia and radiotherapy.

The influence of Co content on the structural and hard magnetic properties of two sets of nanocrystalline Fe 52−x Co x Pt 28 B 20 (x = 0–26) and Fe 60−y Co y Pt 25 B 15 (y = 0–40) alloys was studied. The alloys were prepared as ribbons by the rapid quenching technique. The nanocomposite structure in the alloys was obtained by annealing at 840–880 K for 30 min. Structural characterization of the samples was performed using the Mossbauer spectroscopy and X-ray diffraction. Magnetic properties of the samples were studied by the measurements of the hysteresis loops and of the magnetization at increasing temperatures. An amorphous phase prevailed in the as-quenched Fe 52−x Co x Pt 28 B 20 alloys while a disordered solid solution of fcc-(Fe,Co)Pt was a dominating phase in the Fe 60−y Co y Pt 25 B 15 ribbons. Differential scanning calorimetry measurements revealed one or two exothermic peaks at temperatures up to 993 K, depending on the composition of the alloys. Thermal treatment of the samples led to the formation of the magnetically hard ordered L1 0 tetragonal (Fe,Co)Pt nanocrystallites and magnetically softer phases of (Fe,Co)B (for Fe 52−x Co x Pt 28 B 20 ) or (Fe,Co) 2 B (for Fe 60−y Co y Pt 25 B 15 ). Detailed Mossbauer spectroscopy studies revealed that cobalt substituted for iron in both the L1 0 phase and in iron borides. The nanocomposite Fe 60−y Co y Pt 25 B 15 alloys exhibited significantly larger magnetic remanence and maximum energy products but a smaller coercivity than those observed for the Fe 52−x Co x Pt 28 B 20 alloys. Co addition caused a reduction of the magnetization and the energy product in both series of the alloys. The largest magnetic remanence of 0.87 T and the highest energy product (BH) max = 80 kJ/m 3 were obtained for the Co-free Fe 52 Pt 28 B 20 alloy while the largest coercivity (H C > 950 kA/m) was observed for the Fe 50 Co 10 Pt 25 B 15 and Fe 30 Co 30 Pt 25 B 15 alloys. Differences in the hard magnetic properties of the nanocomposite alloys were related to different phase compositions influencing the strength of inter-phase exchange coupling interactions.

Iron oxide-based nanoparticles have been modified in their core with holmium(III) in an amount affecting only slightly their magnetic properties. Nanoparticles were conjugated covalently with biomolecule of trastuzumab (Herceptin&reg, ), the monoclonal antibody that recognizes cancer cells overexpressing HER2 receptors targeting such nanoparticles to the specified tumor tissues. Systematic studies of Ho3+-doped bioconjugates were carried out as a preliminary step for future replacement of &lsquo, cold&rsquo, Ho with 166Ho radionuclide, emitting &lsquo, soft&rsquo, beta(-) radiation for possible targeted radionuclide therapy. Physicochemical properties of the obtained bioconjugates were subsequently tested for use in magnetic hyperthermia, considered as an effective, low-invasiveness anticancer therapy. With such a system we expect to achieve both: active targeting and multimodal action by simultaneous internal and localized irradiation and magnetic hyperthermia of specific cancers.

We have investigated the effect of gadolinium doping on the structural and electrical properties of Pr0.5−x Gd x Sr0.5MnO3(x=0.0−0.1) manganites. Our samples have been elaborated using the solid-state reaction, at high temperature. Rietveld refinement of the X-ray diffraction patterns has shown that all our samples are single phase and crystallize in the orthorhombic structure with Pbnm space group. Scanning electron microscopy (SEM) revealed that the grains are irregularly spherical-like shaped with mean sizes of 380, 450, and 460 nm for x=0,0.05, and 0.1, respectively. Increasing Gd content enhances electrical resistivity values. Extrinsic magnetoresistance is observed at low temperature.

The monovalent potassium doped manganites Pr 0.6 Sr 0.4− x K x MnO 3 ( x = 0.05–0.2) are characterized using the complementary magnetic susceptibility and electron resonance methods. In paramagnetic phase the temperature variations of the inverse magnetic susceptibility and the inverse intensity of resonance signal obey the Curie–Weiss law. A similarity in temperature variation of resonance signal width and the adiabatic polaron conductivity points to the polaron mechanism controlling the resonance linewidth. The low temperature limit of the pure paramagnetic phase is determined from the electron resonance spectra revealing the mixed phase spread down to the Curie temperature.

Effect of monovalent Na doping on the magnetic properties is studied in Pr0.6Sr0.4−xNaxMnO3 system (x = 0, 0.05) using X-band electron magnetic resonance and magnetization measurements. Temperature variation of magnetic resonance spectra of doped and undoped manganites is analyzed for paramagnetic and ferromagnetic states and compared to similar systems. In paramagnetic phase the magnetic susceptibility proportional to resonance signal intensity is found to obey the Curie–Weiss law. The effective magnetic moment becomes smaller in doped manganite. The paramagnetic Curie temperature derived from signal intensity equals to 312 and 306 K for the undoped and doped manganites, respectively, and is close to values obtained from magnetization variation in paramagnetic phase. The activation energy determined using the adiabatic small polaron hopping model is higher for the undoped than the doped manganite, which proves that the Na doping slightly reduces the Mn3+/Mn4+ double exchange interactions.

Crystals of PrxLa1−xAlO3 solid solution have been grown by the Czochralski method for the first time, to the best of our knowledge. Crystals with high praseodymium concentration tend to grow spirally. The color of the crystals changes with chemical composition. X-ray diffraction shows an increase of the lattice constants with an increase in lanthanum ion concentration. The thermal conductivity has been investigated in the temperature range from 5 to 300 K. Completely different behavior of thermal conductivity is observed at low temperatures for the investigated crystals, whereas it remains roughly constant at high temperatures. The values of magnetic susceptibility lie within the expected range that could be expected for a paramagnetic material.

The structural, magnetic and electrical transport properties of the Sn-doped TbMnO3 manganites are studied by X-ray diffraction, ac susceptibility, dc magnetization and electrical resistivity measurements. The Sn doping into the Tb and Mn sites of TbMnO3 compresses the unit cell and changes parameters of the antiferromagnetic phase whereas the magnetic moment of Mn are only weakly affected. The electrical resistivity of doped manganites is reduced and the activation energy EA is determined for the thermally activated conduction.

The mechanical alloying method was used to prepare Co 60 Fe 30 Ni 10 and Co 50 Fe 35 Ni 15 alloys from the elemental powders. As X-ray diffraction studies proved the final products of milling were the solid solutions with b.c.c . lattice and the average grain size of about 60 nm. After heating of the alloys up to 993 K, the mixtures of two solid solutions with a b.c.c . and f.c.c . lattices were formed. Annealing of the alloys at 1173 K for 1 h resulted in the formation of solid solutions with an f.c.c . lattice. Mossbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different surroundings of 57 Fe isotopes by Co, Fe and Ni atoms, depending on the chemical composition of the alloy. The most probable atomic configurations were determined on the basis of a local environment model. The results of the macroscopic magnetic measurements testified that Co 60 Fe 30 Ni 10 and Co 50 Fe 35 Ni 15 alloys exhibited relatively good soft magnetic properties.

Single-phased Cu 2+ -substituted spinel-related Li 0.5 Fe 2.5 O 4 was synthesized by sintering a mixture of Cu 2+ -substituted corundum-related α-Fe 2 O 3 and Li 2 CO 3 at 700 °C which is ∼325–400 °C lower than the temperature at which the material is prepared by the conventional ceramic methods. X-ray powder diffraction, X-ray photoelectron spectroscopy, Mossbauer spectroscopy and magnetic measurements were used to characterize the material. In contrast to high-temperature synthetic routes, the present one leads to a Cu + -and Fe 2+ -cation free material, thereby optimizing its technological value. Rietveld refinement of the XRD data favors a structural model in which Cu 2+ substitutes for both Fe 3+ and Li + at the octahedral sites. Mossbauer and magnetic data are consistent with this model if spin thermal reversal and/or spin canting are taken into account for the later.

A family of the Hitperm alloys (Fe 0.5 Co 0.5 ) 1-x-y-z M x B y Cu z (M = Hf, Zr, Nb) produced in an argon atmosphere as amorphous ribbons with 0.025 mm thickness are investigated up to 1200 K. The partial replacement of Fe by Co with optimal Fe 0.5 Co 0.5 ratio increases the Curie temperature of the amorphous phase and the magnetic moment per formula unit. The early stages of crystallization can be observed by magnetization measurements. Alloys subjected to the first controlled crystallization stage are built of bcc-(Fe,Co) nanocrystals that are homegeneously embedded in the amorphous matrix. Mean grain sizes are about 11 nm. These two-phase alloys exhibit good soft magnetic properties with the relatively low coercive fields up to 50 A/m. Hafnium and hafnium/zirconium mixture are found to be the best inhibitors of the nanograin growth resulting in the best soft magnetic parameters. Alloys with niobium exhibit lower thermal stability and higher coercive fields. The correlation between the structure evolution and the magnetic properties is analysed and discussed. Conditions for optimum heat treatment are also determined.

Strontium plumbate SrPbO3−δ samples were obtained by means of high pressure synthesis and studied through the temperature (T) dependences of the resistivity ρ and differential thermoelectric power S. Thus prepared samples demonstrate a much steeper increase of ρ for low T than those synthesized by us and other groups without high pressure application. Moreover, the ρ minimum observed earlier and indicating a proximity to the metal state completely disappeared. The sign of S(T) is positive in the whole T range, contrary to what was observed earlier. Tunnel measurements were carried out using the in situ break-junction technique, revealing a correlation dielectric gap Σ≈1.5–2 eV. The data can be explained if one assumes the existence of both holes and electrons in this oxide. The high pressure application during synthesis leads to higher sample disorder, most probably inducing current carrier localization and a Coulomb gap emergence in the quasiparticle spectrum. Electrons do not survive this process, whereas the former minority holes reveal themselves in thermoelectric measurements. Meanwhile, the overall transport behaviour loses its semimetallic features, characteristic of more conventionally produced lead oxide ceramics. Our results show how fragile the electron spectrum of this oxide is, being near the metal–semiconductor phase transition boundary.

We consider tunnelling between a metal partially gapped by charge density waves (CDWM) and an ordinary metal (M) or a ferromagnet (FM) separated by an insulator (I) in an external magnetic field H. Zeeman paramagnetic splitting is assumed to dominate in the CDWM over orbital magnetic effects. The quasiparticle tunnel current J and relevant differential conductance G are calculated as functions of the bias voltage V. The peaks of G(V), originating from the electron density of states singularities near the charge density wave gap edges, were shown to be split in the magnetic field, each peak having a predominant spin polarization. This effect is analogous to the H-induced splitting of G(V) peaks obtained by Tedrow and Meservey for junctions between normal metals and superconductors (S). Thus, it is possible to electrically measure the polarization of current carriers in such a set-up, although the behaviours of G(V) in the two cases are substantially different. The use of M–I–CDWM junctions instead of M–I–S ones has certain advantages. The absence of the Meissner effect, which weakens the constraints upon the junction geometry and electrode materials, comprises the main benefit. The other advantage is the larger energy range of the charge density wave gaps in comparison to that for superconductors' gaps, so that larger Hs may be applied.

Polycrystalline La0.75-xGdxCa0.25MnO3 samples (x=0, 0.10, 0.25, 0.33, 0.50, and 0.75) were prepared by the carbonate precipitation method. For a comparison the nanocrystalline samples with the same compositions were obtained by sol-gel method using urea as gelation agent. The XRD patterns were indexed in orthorhombically distorted perovskite-type unit cell. The unit cell volume steadily decreases with rising Gd content. Magnetic properties of La0.75-xGdxCa0.25MnO3 systems are discussed and compared to other magnetoresistive systems.

Solid solutions Sr 1-x La x PbO 3-δ with x = 0, 0.05, 0.1. 0.15, 0.2 and 0.25 were synthesized by oxalate precursor coprecipitation methods. The solid solutions obtained were analyzed by the XRD technique and iodometric titration. Resistivity p and thermoelectric power S were measured for temperatures 20 K < T < 300 K. The parent compound SrPbO 3-δ shows a shallow minimum of p(T) at about 120 K, whereas p(T) for the La-doped samples are rather smooth with weakly manifested inflection points for all investigated compositions. The thermoelectric power is negative. The transport data demonstrate that the ceramic samples Sr 1-x La x PbO 3-δ are unstable towards electron spectrum dielectrization or localization of current carriers. From the analysis of the measured properties it may be inferred that the effects of disorder and granularity and the inter-grain tunneling, in particular, strongly influence transport phenomena.

Single crystals of La1−xBaxMn1−yCoyO3 (0.26 ≤ x ≤ 0.37; 0 ≤ y ≤ 0.31) perovskites were grown by the flux melt technique using the BaO–B2O3–BaF2 ternary system as a solvent. It was found that the cobalt content in the crystals is determined by the average oxidized state of the manganese ions and depends nonlinearly on the molar ratio of Co/Mn in the initial mixture. All the crystals exhibit ferromagnetic behaviour at low temperatures as well as a jump of resistivity and a magnetoresistance peak around the Curie temperature, gradually decreasing as the cobalt content increases. The low-temperature ferromagnetic phase transforms from the metallic to the semiconducting state with increase in cobalt content.

New ceramics of Sr 1− x K x PbO 3− δ with x =0, 0.05, 0.1, 0.15 and 0.2 were synthesized and analyzed. Temperature, T , variations of resistivity, ρ , and thermoelectric power, S , were measured for 20 T T , the thermal resistivity coefficients d ρ /d T for all compositions were found to be negative, which suggests localization of current carriers or the appearance of a dielectric gap in the electron structure. The analysis of the ρ ( T ) curve shows that the electrical conduction has at least a substantial contribution from the tunneling processes at the grain boundaries. The thermoelectric power S is negative for all compositions and for all T , thus indicating electron-like conduction. The collection of data demonstrates that the parent substance SrPbO 3 is on the verge of the metal–insulator transition and different kinds of doping may substantially change the transport properties and the degree of current carrier degeneracy. The system seems to be promising as a building block for new superconducting families.

Spinel-related magnesium-doped Li 0.5 Fe 2.5 O 4 has been synthesised by heating magnesium-substituted corundum-related α-Fe 2 O 3 with Li 2 CO 3 at 600°C which is ca. 600°C lower than the temperature normally used to prepare metal-doped Li 0.5 Fe 2.5 O 4 by conventional sintering methods. Rietveld structure refinement of the X-ray powder diffraction data shows that the Mg 2+ ions substitute for Fe 3+ ions on the tetrahedral sites whilst the Li + ions are located on the octahedral sites. The 57 Fe Mossbauer spectrum and magnetic measurements are consistent with this structural model.

Samples of the Fe80Ni20 alloys were synthesized in the low energy conventional horizontal and high energy planetary ball mills. Both in the low and high energy processes, the solid bcc Fe(Ni) solutions with a similar structure are formed. The lattice constants are slightly larger than for the pure iron. Thermal stability of alloys was measured upto 1100 K. The magnetization and ferromagnetic Curie temperatures confirm a ferromagnetic ordering. The magnetic moment equal to 2.07 μB for the longest milling periods proves that the electronic structure of the crystalline alloy with nanometer-sized grains does not differ from that of polycrystalline samples. The distributions of the hyperfine magnetic fields revealed that an iron atom has one to two Ni atoms in the nearest neighborhood.

The grain size distribution of copper and nickel processed by severe plastic deformation was studied by transmission electron microscopy. The temperature dependence of electrical resistivity in the temperature range from 20 to 300 K is presented. The tunnel model of electrical resistivity of grain boundaries is discussed. The width of the potential barrier at grain boundaries in copper and nickel is determined. Larger values of potential barriers are noted in ultrafine grained materials in comparison to the crystallographic width of grain boundaries.

We report the electrical resistivity and thermoelectric power of polycrystalline Pb-doped Bi 2:2:2:3 superconductors. In particular the mixed-state properties are investigated by measuring the longitudinal and transverse (Nernst) thermoelectric power. For the first time we show the presence of hysteresis in a high magnetic field for the Nernst effect. We discuss the variation with magnetic field in the properties with respect to the zero-field case and show the power-law behaviour with exponents depending on the transport quantity. We extract 'derived properties' such as the effective mass, the transport entropy, the Ginzburg-Landau parameter, the thermal Hall angle and the activation energy and compare them with previous data on related systems.

The magnetic susceptibility of the tungsten intermediary oxides WO3-x (0.05

Studies of the positron annihilation and the Seebeck effect were performed on silver-doped tungsten trioxide of composition Ag0.01WO3, on the substoichiometric tungsten trioxide phase WO2.975 and on WO2.90(W20O58). Both methods point out that there are some clusters of Ag+ ions in the first case and oxygen vacancies in the second case. The clusters have some internal substructure and the formation enthalpy of the vacancy (or a positron trap) in this substructure was obtained as equal to 0.39+or-0.01 eV. The measurements of the Seebeck effect showed that Ag0.01WO3 and WO2.975 are normal n-type semiconductors whereas WO2.90 exhibits metal-like properties.

The structural, magnetic and electrical transport properties of the Sn-doped TbMnO3 manganites are studied by X-ray diffraction, ac susceptibility, dc magnetization and electrical resistivity measurements. The Sn doping into the Tb and Mn sites of TbMnO3 compresses the unit cell and changes parameters of the antiferromagnetic phase whereas the magnetic moment of Mn are only weakly affected. The electrical resistivity of doped manganites is reduced and the activation energy EA is determined for the thermally activated conduction.

Polycrystalline solid solutions Sr1−xKxPbO3−yFy (0 ≤ x, y ≤ 0.20) were synthesized. Their structural properties were determined by X-ray diffraction. Resistivity and thermoelectric power were measured as functions of temperature. It was shown that a simultaneous substitution of potassium for strontium and fluorine for oxygen results in a transformation of conductivity from semiconductive to metallic at low temperatures. The results are discussed in connection with possible superconductivity in new families of doped perovskites.

Investigations of the temperature dependence of magnetization of amorphous rapidly quenched alloys AxCo80−xB20 (A = B, Al, Si, and Ni) reveal that a substitution of Co by Al and Si atoms causes a faster suppression of magnetization as compared with the Ni substituted alloys. A temperature variation of the electrical resistivity shows that its structural component dominates over the magnetic one. A overwhelming diffusional contribution to the thermoelectric power is found. Untersuchungen der Temperaturabhangigkeit der Magnetisierung von amorphen, schnell abge-schreckten kxCo80−xB20 (A = B, Al, Si und Ni)-Legierungen zeigen, das eine Substitution von Co durch Al- und Si-Atome eine schnellere Unterdruckung der Magnetisierung im Vergleich mit Ni-substituierten Legierungen verursacht. Eine Temperaturanderung des elcktrischen Widerstands zeigt, das seine strukturelle Komponente uber die magnetische dominiert. Ein uberwiegender Diffusionsbeitrag zur Thermospannung wird gefunden.

The electronic industry is engaged in developing Pb-free technologies for more than ten years. However till now not all properties of new solders are described. The aim of the paper is to present some electrical properties of new series of Pb-free solders (eutectic SnAg, near eutectic SnAgCu with and without Bi) in low temperature ranges 10 K to 273K. The following parameters were analyzed: electrical resistivity, temperature coefficient of resistance and thermoelectric power. The electrical resistivity at temperatures above 50 K is a monotonically rising function of temperature for Pb-free solders studied. The electrical resistivity of the Bi containing alloys is higher as compared to the remaining ones. The thermoelectric power values at room temperature are about -8 μV/K to -6 μV/K for Pb-free solders studied, being higher as compared to typical values -3 μVK of SnPb solder. The relatively low absolute values as well as the smooth and weak temperature variation of electrical resistivity in lead free solders enable the possible low temperature application. The moderate values of thermoelectric power around and above the room temperature show that when applying the solders studied the temperature should be kept as uniform as possible, in order to avoid spurious or noise voltages.

Magnetic properties of nanocrystalline Fe78B13Si9 alloys are studied for three seriesprepared by ball milling starting from amorphous ribbons, crystallized ribbons, and elementalpowders. Temperature variation of static magnetization results in strong ferromagnetic interactionwhich is weakly dependent on the initial material. Magnetic hysteresis loops show that saturationmagnetization, magnetic remanence, and coercive field increase with frequency for both series ofribbon samples, whereas they decrease for alloys prepared from elemental powders. Power lossesraise faster for the alloys prepared from elemental powders than for the two other alloys.

Temperature, T, variations of the tunnel conductance G(V) were calculated for junctions between a normal metal and a spatially inhomogeneous superconductor with a dielectric gap on the nested sections of the Fermi surface or between two such superconductors. The dielectric gapping was considered to be a consequence of the charge density wave (CDW) appearance due to the electron–phonon (for a Peierls insulator) or a Coulomb (for an excitonic insulator) interactions. Spatial averaging was carried out over random domains with varying parameters of the CDW superconductor (CDWS). The calculated tunnel spectra demonstrate a smooth transformation from asymmetric patterns with a pronounced dip–hump structure at low T into those with a pseudogap depletion of the electron densities of states at higher T in the vicinity or above the actual critical temperatures of the superconducting transition for any of the CDWS domains. Thus, it is demonstrated that both the dip-hump structure and pseudogapping are manifestations of the same phenomenon. A possible CDW-induced asymmetry of the background contribution to G(V) is also touched upon. The results explain the peculiar features of G(V) for Bi2Sr2CaCu2O8+δ and other related high-Tc cuprates.

Polycrystalline samples of semiconducting θ-iron vanadium oxide bronzes FexV2O5 (x = 0.33 to 0.37) are studied from 4.2 to 600 K revealing spin glass and paramagnetic ranges. The transition is observed by static susceptibility, ESR, and Mossbauer effect measurements and is discussed in terms of magnetic clusters formed by iron atoms. The spin glass order parameter and its temperature variation is evaluated. In polykristallinen Proben der halbleitenden Bronzen θ-FexV2O5 (x = 0,33 bis 0,37), die zwischen 4.2 und 600 K untersucht werden, werden Spinglas-Bereiche und paramagnetische Bereiche gefunden. Der Ubergang wird mittels statischer Suszeptibilitat, ESR sowie Mosbauer-Effekt beobachtet und im Rahmen des Modells der magnetischen Kluster der Eisenatome diskutiert. Der Spinglas-Ordnungsparameter und seine Temperaturabhangigkeit werden abgeschatzt.

The 57Fe Mossbauer spectra of the vanadium oxide bronze θ-Fe0.35V2O5 recorded between 4 and 524 K reveal below 17 K the ordered magnetic phase of the spin-glass type and the paramagnetic one at higher temperatures. The two observed quadrupole doublets with nearly the same isomer shift but different ΔEQ values are due to the Fe3+ ions occuring in two inequivalent surroundings. Calculations of the electric field gradient (EFG) show that the lower value of ΔEQ may be ascribed to the distorted octahedral coordination of the Fe atom whereas the higher value of ΔEQ is due to the Fe atom in the adjacent site which may be randomly occupied.