The magnetic properties of spinel nanoparticles are determined by crystal chemistry issues such as cation distribution and oxidation states. The cation distribution and oxidation state of Mn-Fe spinel nanoparticles have been systematically studied at various temperatures by using neutron diffraction and electron energy loss spectroscopy, respectively. The Mn-Fe spinel nanoparticles prepared by ...

High pressure/temperature annealing experiments are used to determine diffusivities of H and D in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth’s mantle. Data are fitted to the following Arrhenius law: Diffusivity (m/s) = 4 ± 1 × 10 exp(−54 ± 2 kJ mol/RT). At low temperatures, H and D diffusion in non-stoichiometric spinel is charge balanced by flu...

[1] We present details of the identification of sites that show an absorption band at visible wavelengths and a strong 2 m band using the SELENE Spectral Profiler. All the sites exhibiting the visible feature are found on the regional dark mantle deposit (DMD) at Sinus Aestuum. All the instances of the visible feature show a strong 2 m band, suggestive of Feand Cr-rich spinels, which are differ...

Li-rich layer-structured cathode thin films are prepared by pulsed laser deposition. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS) and electrochemical testing in half battery cells are used to characterize crystal structure, surface morphology, chemical valence states and electrochemical performance of these thin films, resp...

Magnetic measurements were carried out on different samples of Lithium-Manganese spinel LiMn 20 4 , great care having been taken to avoid the presence of spurious magnetic phases, such as Mn 3 0 4 . Susceptibility data, showing deviations from paramagnetic behaviour at about 40 K, were analyzed in terms of local magnetic interactions, taking into account the structural and transport properties ...

The mechanical properties (fracture strength, fracture toughness, and Vickers microhardness) of MgAl2O4 and x wt% ZrO2–MgAl2O4 (1 # x # 30) hot-pressed materials were measured at room temperature. Two kinds of materials, which were prepared from either ball-milled or attrited powders, were investigated. Compared with an unreinforced spinel, a twofold (or greater) increase in both strengthening ...

Reduction of polycrystalline and crystalline magnesium orthovanadate Mg V O by hydrogen was investigated in the temperature 3 2 8 range of 560–9208C. A single crystal of orthorhombic Mg V O with a cation-deficient-spinel structure (25% of the magnesium atoms on 3 2 8 octahedral sites are vacant) was transformed into cubic Mg V O which has a cation-stuffed-spinel structure (8a and 16c sites were...

This book chapter is organized into four major parts. Firstly, it will cover an introduction of using spinel ferrite nanoparticles in biomedical applications, including the antibacterial properties. The second part will provide an overview of the structure and magnetism of spinel ferrites. The third part will focus on the preparation of cobalt ferrite and transition metal substituted cobalt fer...

Simple algebraic equations show that the bulk compressibility in spinel-type compounds can be expressed by means of cation oxide polyhedral compressibilities and a term that accounts for the pressure effect on the internal oxygen position in the unit cell. The equations explain ~i! the difference of compressibilities at octahedral and tetrahedral sites, ~ii! why the macroscopic bulk modulus can...