The magnetotransmission, magnetoreflection, and magnetoresistance of the La0.7Ca0.3MnO3 and La0.9Ag0.1MnO3 epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

Complex experimental investigations of the structural, optical, and magneto-optical properties (magnetotransmission, magnetoreflection, and transversal Kerr effect, as well as the magnetoresistance, of La0.7Ca0.3MnO3 epitaxial films indicate that magnetoreflection and magnetotransmission in manganite films can reach giant values and depend strongly on the magnetic and charge homogeneity of the films, their thickness, and spectral range under investigation. It has been shown that the optical enhancement of the magnetorefractive effect occurs in thin films as compared to manganite crystals. In the region of the minimum of the reflectance near the first phonon band, the resonance-like magnetorefractive effect has been observed, which is accompanied by change of the sign of the magnetoreflection. A model based on the theory of the magnetorefractive effect has been proposed to qualitatively explain this behavior.

For the first time the (001)-oriented Sr-based (Hg,Pb)-1223 films have been synthesized using the two-step procedure. Hg-free precursor films with the thickness of 1 μm have been deposited by MOCVD or PLD and then the films were annealed in sealed quartz ampoules together with synthesised (Hg,Pb)-1223 ceramics or a pressed precursor mixture of the same cation composition. No post-annealing in oxygen was used for these films. The phase composition of the PLD-films depended crucially on the deposition temperature of the precursor films. The best MOCVD films contained predominantly (Hg,Pb)-1223 and small amounts of non-superconducting phases according to XRD. The T c =118 K and j c (77K,0.01T) = 2.5×10 6 A/cm 2 were measured for the MOCVD-samples.

The effect of 16O → 18O oxygen isotope substitution has been studied for (Pr1−y Eu y )0.7Ca0.3CoO3 cobaltites (0.12 < y < 0.26). A pronounced isotope shift has been found for the spinstate transition temperature, which increases with the oxygen isotope mass. In contrast, the ferromagnetic transition temperature has slightly lower values for the samples with heavier oxygen. The observed phenomena and constructed phase diagram confirm the results reported previously for (Pr1 − y Sm y )0.7Ca0.3CoO3 in [G. Y. Wang, X. H. Chen, T. Wu, et al., Phys. Rev. B 74, 165113 (2006)]. The measurements of the specific heat have been performed for (Pr1 − y Eu y )0.7Ca0.3CoO3 with the main emphasis on the analysis of the isotope effect. The contributions to the isotope effect coming from the lattice and magnetic components of the specific heat have been separated. The mechanisms underlying the large isotope effect are discussed.

We present the study of magnetization, thermal expansion, specific heat, resistivity, and a.c. susceptibility of (Pr$_{1-y}$Eu$_y$)$_{0.7}$Ca$_{0.3}$CoO$_3$ cobaltites. The measurements were performed on ceramic samples with $y = 0.12 - 0.26$ and $y = 1$. Based on these results, we construct the phase diagram, including magnetic and spin-state transitions. The transition from the low- to intermediate-spin state is observed for the samples with $y > 0.18$, whereas for a lower Eu-doping level, there are no spin-state transitions, but a crossover between the ferromagnetic and paramagnetic states occurs. The effect of oxygen isotope substitution along with Eu doping on the magnetic/spin state is discussed. The oxygen-isotope substitution ($^{16}$O by $^{18}$O) is found to shift both the magnetic and spin-state phase boundaries to lower Eu concentrations. The isotope effect on the spin-state transition temperature ($y > 0.18$) is rather strong, but it is much weaker for the transition to a ferromagnetic state ($y < 0.18$). The ferromagnetic ordering in the low-Eu doped samples is shown to be promoted by the Co$^{4+}$ ions, which favor the formation of the intermediate-spin state of neighboring Co$^{3+}$ ions.

Strained epitaxial BiFeO3 films deposited on (001) SrTiO3 substrates by metal organic chemical vapor deposition were studied by optical second harmonic generation (SHG) and SQUID magnetometry. The observed SHG intensity vs temperature dependencies indicate that for less strained films (σ<0.6GPa) a strong interplay between the ferroelectric and magnetic subsystems exists, while for the films with larger σ-values strain-induced destruction of the magnetic cycloidal ordering takes place.

The magnetic/spin-state phase diagram of the (Pr1-yEuy)0.7Ca0.3CoO3 series was obtained on the basis of measurements of the specific heat, thermal expansion, magnetization and resistivity. The phase diagram reveals three different states depending on the static distortions (Eu content), the oxygen-isotope mass, and the temperature. The samples with the lower Eu concentrations are ferromagnetically ordered up to moderate temperatures (about 50 K),, most probably, due to the low-spin Co4+ – intermediate-spin Co3+ interaction of the double-exchange type. As the Eu doping increases, the Co3+ LS (S = 0) state becomes stabilized and the magnetic ordering of the Co4+ ions is suppressed up to temperatures well below 5 K, resulting in a low-temperature anomaly in Cp. At higher temperatures, we observe a first-order spin-state transition from the LS to the IS state of Co3+, which is accompanied by a decrease in the electrical resistivity, an increase in the magnetization, and a strong lattice expansion.

The growth of epitaxial CaF(2) and SrF(2) thin films on single crystalline r-cut sapphire, MgO (001) and biaxially textured Ni-W polycrystalline tape by low-temperature MOCVD is reported. A novel and efficient combination of alkaline-earth and fluorine precursors was used for deposition. A comprehensive study regarding the out- and in-plane orientation of the films and their surface morphology is presented using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), energy-dispersive X-ray analysis (EDX), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and electron backscatter diffraction (EBSD). The grown films are shown to have different crystallographic orientation depending on the film-substrate lattice mismatch and growth rate. Both types of films were obtained with pure c-axis orientation on all used substrates by either choosing the appropriate deposition conditions or postdeposition treatment. Epitaxial relations for all grown films are determined. A film-substrate interaction is described for the case of Ni-W substrate; a way to avoid it is proposed and successfully implemented. Certain growth conditions are shown to result in a unique three-dimensional ordered nanogrid structure of the films, making them perfect nanotemplated substrate for the epitaxial growth of other functional layers.

The early stages of surface oxidation of biaxially textured Ni-W tapes were studied using thermodynamic calculations along with experimental tape oxidation at low P(O2). Tape phase and chemical composition, surface morphology, and roughness were examined using x-ray diffraction (XRD), energy-dispersive x-ray analysis (EDX), secondary ion mass spectroscopy (SIMS), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For a Ni0.95W0.05 alloy tape, the precise position of the tape oxidation line in P(O2)-T coordinates was established. This line includes a break at T ≈ 650 °C that originates from the change of the W oxidation mechanism from internal oxidation to oxidation on a free surface accompanied by segregation of the alloy components in the tape near-surface region. The surface roughness of a polished tape increased drastically during internal oxidation of W; further tape oxidation did not affect the integral roughness parameters, but introduced numerous small (~100 nm) features on the tape surface comprising NiO precipitates.

The low-temperature minimum of the resistivity of La0.85Ag0.15MnO3 is investigated in detail. Analysis of the experimental data shows that the observed low-temperature minimum of the zero-field resistivity and the large magnetoresistive effect, which increases with decreasing temperature, can be explained in a model of spin-polarized tunneling of charge carriers through grain boundaries.

For a series of epitaxial and polycrystalline manganite/ferrite heterostructures grown on different substrates, the interelation between light transmission in the IR range and electrical resistance, magnetotransmission, and magnetoresistance has been studied in a temperature range of 80–385 K. It has been established that the temperature dependences of transmission and magnetotransmission in the manganite/ferrite heterostructures on different substrates are similar to the temperature dependences in the films of manganites on the same substrates. It has been shown that in a magnetic field of 8 kOe applied perpendicular to the surface of the epitaxial manganite/ferrite heterostructure the magnetotransmission increases by ∼40% relative to its value in the single-layer epitaxial films.

Thin films of alkali-earth fluorides and multilayer structures including such layers are known as perspective materials for optics, photonics and chemical sensors. They can also be considered as a material for buffer layers for 2G HTSC wires. Here we report on growing epitaxial CaF2 and SrF2 films on different substrates by MOCVD. The films' properties were examined using RBS, SEM, EDX, XRD, EBSD and AFM. The obtained films revealed perfect in- and out-of-plane orientation and had a smooth, crack-free surface. Depending on the substrate and deposition conditions, some films required the recrystallization annealing to form the epitaxial layer or that of good texture. Additionally, a number of multilayer films including MF2 layers were grown. The obtained films were successfully used as substrates for HTS deposition.

The low-temperature minimum of the La0.85Ag0.15MnO3 resistivity has been investigated. The analysis of the experimental data shows that this minimum of resistivity in zero magnetic field and the large magnetoresistive effect, which increases with a decrease in temperature, can be explained within the model of spin-polarized tunneling of carriers through grain boundaries.

Temperature and frequency dependencies of the real (χ′) and imaginary (χ″) parts of the dynamic magnetic susceptibility were studied experimentally in fine particles of La–Ag manganites prepared by various methods. The samples under study have the Curie points in the range TC=42–48°C, which is a medical hyperthermia range of interest. When approaching TC from below, a critical peak of χ″ was revealed, followed by a steep drop while passing to the paramagnetic phase. The experiments on the magnetic radio-frequency (RF) heating of the manganite aqueous suspensions demonstrated good autostabilization of the temperature near TC. Peculiar instability is found in the heating kinetics, caused by the observed critical behavior of the RF losses. The prospects of the La–Ag manganites as candidates for application in the temperature-controlled hyperthermia are discussed.

An investigation of the critical behavior of the specific heat of the manganites La1−xAgxMnO3 ×(x=0.1,0.15,0.2) near the Curie temperature is carried out. The behavior of the universal critical parameters near the phase transition point is established. All of the samples studied correspond to the ferromagnetic Heisenberg 3D universality class of critical behavior, with the critical exponent α=−0.115, −0.106, and −0.106 for La0.9Ag0.1MnO3, La0.85Ag0.15MnO3, and La0.8Ag0.2MnO3, respectively. It is shown that the universality class of the critical behavior of the specific heat of the manganites La1−xAgxMnO3 is independent of the silver concentration.

This work aimed to analyze the possibility and performance of the temperature controlled hyperthermia based on AC heating of magnetic nanoparticles with low Curie temperature. Temperature dependence of dynamic magnetic susceptibility has been studied experimentally on fine powders of La0.8Ag0.15MnO2.95 in the frequency range of 0.5–2.0 MHz. Critical drop of the AC magnetic losses was found in the vicinity of the Curie point, TC = 42°C. The obtained data was used in the numerical analysis of the bioheat equations under typical conditions of the hyperthermia treatment. The mathematical model includes a spherical tumor containing magnetic particles and surrounded by concentric healthy tissue, with account made for the blood perfusion. The calculations performed for various AC power, tumor sizes and doping geometries predict effective autostabilization of the temperature at T ≅ TC inside the tumor and steep temperature profile at the interface with the healthy tissue.