14 research outputs found
Hole-doped, High-Temperature Superconductors Li_{x}BC, Na_{x}BC and C_{x} : A Coherent-Potential-Based Prediction
Using density-functional-based methods, we show that the hole-doped
Li_{x}BC and Na_{x}BC in P6_{3}/mmc crystal structure and C_{x} in graphite
structure are capable of showing superconductivity, possibly with a T_{c} much
higher than that of
MgB_{2}. We use full-potential methods to obtain the optimized lattice
constants a and c, coherent-potential approximation to describe the effects of
disorder, Gaspari-Gyorffy formalism to obtain the electron-phonon coupling
constant , and Allen-Dynes equation to calculate T_{c} as a function
of hole concentration in these alloys.Comment: 4 pages, 5 figure
Structure of macrodomain walls in polytwinned magnets
We propose a microscopic approach to the studies of magnetic configurations in hard magnets which may be conveniently used for nanoscale systems; the microstructure of the magnet is easily and naturally included in the calculations. This approach is applied to find the structure of macrodomain walls in polytwinned magnets of the CoPt family. Magnetostatic fields are small compared to the anisotropy field in these magnets; direct simulation shows that in this case the macrodomain wall is not continuous, but rather comprised of segments held together by relatively small magnetostatic forces. This segmentation is expected to have a strong effect on magnetization processes