Application of magneto-optical method for detection of material structure changes

The possibilities of magneto-optical sensors to control the damage of ferromagnetic and para-magnetic materials and products are considered. In the introduction it is shown that modern magneto-optical materials used in creating sensors have a high sensitivity and spatial resolution. So, on their basis it is possible to develop sensitive and informative means of non-destructive testing for a wide range of applications. For example, it is used to detect microcracks, corrosion damage, degradation changes in the material structure, surface deformations, and subsurface defects. The method ability to detect appearance of magnetic phases in paramagnetic materials, that are precursors of fracture, is of a special importance. The advantage of magneto-optic sensors is a large observation area and high spatial resolution. Resolution of the sensor is determined by the period and size of the domain structure, which averages 13...50 micrometres. High sensitivity of the sensor is due to a small saturation field of the magneto-optic material from 0.1 mT to 0.7 mT. In addition, these parameters are controlled by changing the temperature of the sensor, direction and intensity of the magnetic field. In this paper an optical scheme based on magneto-optical garnet film for visualization of fatigue cracks, which are formed in compact samples during their experimental investigation on fatigue failure is described. The developed scheme allowed us to visualize and fix position of the crack and determine its actual length, considering the closed part of the crack. A further direction of research will be to increase the sensitivity of the developed scheme and reduce the noise of magneto-optical images to identify the initial stages of the degradation process of ferromagnetic and paramagnetic materials and products.

Synthesis, characterization and effect of dopant on magnetic hyperthermic efficacy of Gd2O3 nanoparticles

Rare-earth oxides are paramagnetic materials and their high magnetic susceptibility in the bulk makes them potentially promising materials, but the magnetic properties of their nanoparticles remain incompletely characterized. We explore the effect of dopant (Tb3+ and Eu3+) in Gd2O3 host lattice as a heating agent for magnetic hyperthermia application. The structural, optical, and magnetic properties of the pristine, Gd2O3:Tb3+ and Gd2O3:Eu3+ nanocrystals were studied by XRD, HR-TEM, FTIR, and VSM. XRD analysis revealed the presence of mixed phase (cubic and monoclinic) in pristine, and doped Gd2O3 nanoparticles. The morphological information has been observed with the help of HRTEM and the calculated inter-planar spacing is in well agreement with JCPDS data. Particles are nearly spherical and diameter ~15nm, estimated from HRTEM image. FTIR spectroscopic analysis confirms the presence of Gd-O-Gd stretching at 583cm-1 . We confirmed the paramagnetic nature for all samples using VSM analysis. The self-heating capability of prepared samples are investigated by performing the induction heating experiment and it is assessed through calculated SAR and ILP values with help of Box-Lucas fitting model where 10% Tb3+ doped Gd2O3 has maximum values.

Synthesis of holmium orthoferrite nanoparticles by the co-precipitation method at high temperature

Holmium orthoferrite HoFeO3 nanoparticles were synthesized by a simple co-precipitation method via the hydrolysis of Ho (III) and Fe (III) cations in boiling water with 5% aqueous ammonia solution. After annealing the precipitate at 750 and 850 °C for 1 hour, the single-phase HoFeO3 product formed with particle size < 50 nm. The synthesized nanopowders are paramagnetic materials with remanent magnetization Mr < 0.01 emu·g-1, the coercive force Hc = 20÷21 Oe, and magnetization Ms ~ 2.73 emu·g-1 at 300 K in a maximum field of 16,000 Oe.

Boltzmann Statistics

When a system is held at a fixed temperature, its higher-energy states are less probable than its lower energy states by an amount that depends on how the energy compares to the temperature. The formula that quantifies this idea is called the Boltzmann distribution. This chapter derives the Boltzmann distribution and shows how to use it to predict the thermal behavior of any system whose microscopic states we can enumerate. The examples go beyond the three simple model systems studied already in Chapters 2 and 3 to include detailed properties of gases, stellar spectra, and paramagnetic materials.

Paramagnetic and Diamagnetic Susceptibility of Infinite Quantum Well

Paramagnetism and diamagnetism of a material characterized by its magnetic susceptibility. When a material is exposed to an external magnetic field, magnetic susceptibility is defined as the ratio of the induced magnetization and the magnetic field. A paramagnetic material has magnetic susceptibility with positive sign. On the other hand, a diamagnetic material has magnetic susceptibility with negative sign. Atomically, paramagnetic materials consist of atoms that has orbital with unpaired electrons. Theoretical study of paramagnetic susceptibility and diamagnetic susceptibility are well described by Pauli paramagnetism and Landau diamagnetism, respectively. Although paramagnetism and diamagnetism are among the simplest magnetic properties of material that are studied in basic physics, theoretical derivations of Pauli paramagnetic and Landau diamagnetic susceptibility require second quantization formalism of quantum mechanics. We aim to discuss the paramagnetic and diamagnetic susceptibilities for simple three-dimensional quantum well using first quantization formalism.

The Synthesis and Characterization of Sol-Gel-Derived SrTiO3-BiMnO3 Solid Solutions

In this study, the aqueous sol-gel method was employed for the synthesis of (1−x)SrTiO3-xBiMnO3 solid solutions. Powder X-ray diffraction analysis confirmed the formation of single-phase perovskites with a cubic structure up to x = 0.3. A further increase of the BiMnO3 content led to the formation of a negligible amount of neighboring Mn3O4 impurity, along with the major perovskite phase. Infrared (FT-IR) analysis of the synthesized specimens showed gradual spectral change associated with the superposition effect of Mn-O and Ti-O bond lengths. By introducing BiMnO3 into the SrTiO3 crystal structure, the size of the grains increased drastically, which was confirmed by means of scanning electron microscopy. Magnetization studies revealed that all solid solutions containing the BiMnO3 component can be characterized as paramagnetic materials. It was observed that magnetization values clearly correlate with the chemical composition of powders, and the gradual increase of the BiMnO3 content resulted in noticeably higher magnetization values.

Crystal structure, optical and magnetic properties of PrFeO3 nanoparticles prepared by modified co-precipitation method

In this work, PrFeO3 nanoparticles were synthesized by modified co-precipitation method and annealed at different temperatures up to 850?C. The annealed PrFeO3 nanoparticles have single phase orthorhombic structure and the average particle size of 25-30 nm. Due to the very small particle size the prepared PrFeO3 nanoparticles are capable of being used as photocatalyst materials thanks to their strong adsorption bands at 230-400 nm and 400-800 nm observed from the UV-Vis spectra. Additionally, the PrFeO3 nanoparticles are paramagnetic materials with Hc ~ 10Oe and Mr ~ 0. These findings demonstrate their potential use not only as photocatalysts, but also as magnetic materials.

Выращивание и свойства монокристаллов FeIn-=SUB=-2-=/SUB=-S-=SUB=-3.6-=/SUB=-Se-=SUB=-0.4-=/SUB=-

FeIn_2S_3.6Se_0.4 single crystals are grown by planar crystallization of the melt (the vertical Bridgman method). The composition and crystal structure of the crystals are determined. It is established that the single crystals crystallize with the formation of the cubic spinel structure. From the transmittance spectra in the region of the fundamental absorption edge, the band gap of the single crystals is determined. Thermal expansion of the FeIn_2S_3.6Se_0.4 single crystals is studied by the dilatometric technique in the temperature range from 80 to 550 K, and the coefficients of thermal expansion are determined. From the coefficients of thermal expansion determined, the Debye temperatures and the root-mean-square (rms) dynamic displacements of atoms are calculated. It is shown that, as temperature is elevated, the Debye temperatures decrease and the rms dynamic displacements of atoms increase. Magnetic studies show that the FeIn_2S_3.6Se_0.4 single crystals are paramagnetic materials at temperatures down to 12.4 K.