Temperature and magnetic field induced structural transformation in Si doped CeFe2: in-field x-ray diffraction study

Using x-ray powder diffraction technique at various temperatures and applied magnetic fields, we have studied the magnetostructural properties of Ce(Fe0.95Si0.05)2. The x-ray diffraction data establish quantitative relationships between bulk magnetization and the evolution of structurally distinct phases with magnetic field and temperature, and confirm the distinct features of first order phase transition like supercooling and superheating, metastability, and phase co-existence of different structural polymorphs. We observe the lattice volume mismatch across the structural phase transition, which appears to be the cause for the step behavior of the magnetization isotherms at low temperatures. The present study shows that the lattice distortion has to be treated explicitly, like spin, along with the effects of lattice-spin coupling to account for the magnetization behavior of this system. This structure template can resolve the issue of kinetics in this material as observed in different time scale measurements and with different experimental protocols.Comment: 13pages,5 figure

Magnetostructural transition in Ce(Fe0.975Ga0.025)2 compound

The magnetic and magnetostructural properties of the polycrystalline Ce(Fe0.975Ga0.025)2 have been investigated as a function of temperature and magnetic field. In Ce(Fe0.975Ga0.025)2 the magnetic transition from antiferromagnetic (AFM) to ferromagnetic state (FM) is accompanied by a structural transformation from rhombohedral to cubic structure. Phase coexistence is present during both the temperature and field driven transformations from the AFM to FM phase

Structural and magnetothermal properties of the Gd5SbxGe4−x system

The crystallographic and magnetic properties of the Gd{sub 5}Sb{sub x}Ge{sub 4-x} pseudobinary system were studied by x-ray powder diffraction at room temperature, and the heat capacity, magnetization, and electrical resistivity in the temperature interval 5-320 K in applied dc magnetic fields between 0 and 100 kOe. The Gd{sub 5}Sb{sub 2.1}Ge{sub 1.9} compound adopts the Tm{sub 5}Sb{sub 2}Si{sub 2}-type structure (space group Cmca) and orders magnetically via a second order ferromagnetic-paramagnetic transition at 200 K, whereas the Gd{sub 5}Sb{sub x}Ge{sub 4-x} compounds with x=0.7 and x=1 crystallize in the Sm{sub 5}Ge{sub 4}-type structure (space group Pnma) and exhibit first order phase transformations at 45 and 37 K, respectively, and therefore, the giant magnetocaloric effect. The heat capacity and electrical resistivity measurements of Gd{sub 5}Sb{sub 0.7}Ge{sub 3.3} indicate a second order antiferromagnetic transition at 60 K in fields 20 kOe and lower

Психічне здоров’я працівників державних установ

Монографія є результатом колективної роботи з вивчення психічного здоров’я працівників державних установ. У тексті представлено результати теоретичних та емпіричних досліджень. Для психологів, керівників і працівників державних установ, викладачів, аспірантів, студентів, усіх хто цікавиться питанням психічного здоров’я як у повсякденному житті, так і в контексті робочого місця особистості

Structure evolution and dielectric behavior of polystyrene-capped barium titanate nanoparticles

Polystyrene-capped barium titanate (BaTiO3) nanoparticles with sizes of 11 nm and 27 nm were prepared using amphiphilic star-like diblock copolymer templates. The crystal structure evolution of these nanoparticles over a wide temperature range (10-428 K) was investigated by powder X-ray diffraction. The Rietveld refinement indicates that the abrupt structural transitions observed in micron-sized powders become broad as particle size is reduced to a few tens of nanometers. The orthorhombic phase (Amm2) is observed in the range of 10-388 K, coexisting with the rhombohedral phase (R3c) at lower temperatures and with the tetragonal phase (P4mm) at higher temperatures. At room temperature (300 K), polystyrene-capped BaTiO3 nanoparticles, both 11 and 27 nm sizes, primarily adopt the tetragonal phase, transforming to the cubic phase ( Pm3m) at 398 K during heating. The phase evolution of the nanoparticles correlates well with their dielectric behavior. With the Landauer-Bruggeman effective approximation, the dielectric properties at room temperature for the BaTiO3 core were calculated and the results are in agreement with the size effect of BaTiO3 nanocrystals

Thermal expansion and magnetostriction in Pr(n+2)(n+1)Nin(n-1)+2Sin(n+1) compounds

Thermal expansion and magnetostriction of members of a homologous series of compounds based on the alloy series Pr(n+2)(n+1)Nin(n?1)+2Sin(n+1) have been measured. The crystal structures of these compounds are closely interrelated because they form trigonal prismatic columns in which the number of trigonal prisms that form the base of the trigonal columns is determined by the value of n in the chemical formula. Two compositions were investigated, Pr5Ni2Si3 and Pr15Ni7Si10, corresponding to n=3 and n=4, respectively. The results were analyzed and used to determine the location of magnetic phase transitions by calculating the magnetic contribution to thermal expansion using the Gruneisen–Debye theory. This allowed more precise determination of the magnetic transition temperatures than could be achieved using the total thermal expansion. The results show two phase transitions in each material, one corresponding to the Curie temperature and the other at a lower temperature exhibiting characteristics of a spin reorientation transition