Crystal structure magnetic materials

In the ceramics field many of the new advanced ceramic oxides have a specially prepared mixture of cations which determines the crystal structure, through the relative sizes of the cations and oxygen ions, and the physical properties through the choice of cations and tlreh oxidation states. These include, for example, solid electrolytes and electrodes for sensors and fuel cells, fenites and garnets for magnetic systems, zirconates and titanates for piezoelectric materials, as well as ceramic superconductors and a number of other substances... 

W. Giriat and J.K. Furdyna, Crystal Structure, Composition, and Materials Preparation of Diluted Magnetic Semiconductors... 

It is relatively common for DFT calculations to not explicitly include electron spin, for the simple reason that this approximation makes calculations faster. In materials where spin effects may be important, however, it is crucial that spin is included. Fe, for example, is a metal that is well known for its magnetic properties. Figure 8.10 shows the energy of bulk Fe in the bcc crystal structure from calculations with no spin polarization and calculations with ferromagnetic spin ordering. The difference is striking electron spins lower the energy substantially and increase the predicted equilibrium lattice constant by 0.1 A. 

The formation of crystalline fulleride salts at the electrode occurs when less polar solvents and bulky cations are used for the electrosynthesis. The first fulleride salt was synthesized by Wudl by bulk electrolysis of in o-dichlorobenzene with tetraphenylphosphonium chloride as supporting electrolyte [39, 80]. This black microcrystalline material with the composition (Ph4P )3(Cgg )(Cr)2 exhibits an ESR line with a g-value of 1.9991 and a line width of 45 G at room temperature. Single crystals of the slightly different salts (Ph4P )2(Cgg )(Cr) and (Ph4P )2(C50 )(Br ) could be obtained by electrocrystallization and their crystal structure was determined [82, 83]. Magnetic measurements showed the presence of unpaired spins. 

The high hardness of chromium oxide resulting from its crystal structure is exploited in polishing agents for metals and in brake linings. Addition of a small amount of chromium oxide to magnetic materials of audio and video tapes imparts a self-cleaning effect to the sound heads. 

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