In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Simple rules for the understanding of Heusler compounds

and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

Size dependence of nanostructures: Impact of bond order deficiency

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Surface chemistry of catalysis by gold

We present calculations of interband optical conductivity of the compound Ni 3 Al using the linear-muffin-tin-orbital method. Calculations are performed using constant matrix elements and calculated matrix elements. We find that matrix elements play a significant role in influencing the magnitude of optical conductivity σ(ω) and the position of peaks. Since Ni 3 Al is weakly ferromagnetic (magnetic moment equal to 0.31 μ B per unit cell), we have also calculated σ(ω) using the ferromagnetic band structure but without spin-orbit coupling. A comparison of our results with experimental data is presented

Interband optical properties of Ni3Al.

The existence of ferromagnetism in the wonder material graphene has opened up the path for many future spintronics and memory applications. But simultaneously it is very important to understand the variation of these properties with temperature in regards to the device applications. Here we observed defect induced ferromagnetism in chemically reduced graphene and the effect of temperature on it. Several theoretical studies have proved that the main cause of ferromagnetism in graphene is due to various defects. The observed results established that these defects can be mended by treating the samples at elevated temperatures but sacrificing the ferromagnetism simultaneously. Hence, temperature plays a crucial role in controlling the magnetism as well as the defects in graphene. In this study we revealed that at 600 °C the self-repair mechanism helps the defects to mend but resulting in the decrement of magnetization and providing a good quality graphene with less defects.

Temperature tuned defect induced magnetism in reduced graphene oxide

Nanowires for spintronics: A study of transition-metal elements of groups 8–10

We investigated the changes in the electronic structure of Cu, Ag, and Au in going from three-dimensional (3D) to two-dimensional to one-dimensional structure. Compared to 3D case, the interatomic distance (cohesive energy per bond) shows significant drop (rise) as dimensionality decreases. The shallow $d$ bands of 3D become sharper and shallower, and for Cu (Au) reach just below (above) the Fermi level. This picture is very sensitive to the accuracy of the calculations and may affect the calculated properties of nanowires. The spin-orbit interaction is found to play a significant role in Au, altering the electronic structure considerably and increasing the number of conducting channels in 1D Au.

Effect of dimensionality on the electronic structure of Cu, Ag, and Au

The electronic structure and optical properties of the rare earth sesquioxides (R2O3, R=La, Pr, and Nd) have been studied using the full potential linearized augmented plane wave method within local spin density approximation (LSDA) and Coulomb corrected local density approximation (LSDA+U) as implemented in the WIEN2K code. Our calculations show that the LSDA+U results give a better representation of the band structure compared to LSDA. Our calculated reflectivity and optical conductivity spectra are compared with the experimental data. The peaks in the optical conductivity can be explained as arising out of the transitions from R-p and O-p to R-d states. We have also calculated the dielectric function and the coefficient of refraction for these rare earth sesquioxides. We do not find any significant differences in the optical properties calculated using LSDA and LSDA+U.

Tashi Nautiyal

Papers

Interband optical properties of Ni3Al.

Temperature tuned defect induced magnetism in reduced graphene oxide

Nanowires for spintronics: A study of transition-metal elements of groups 8–10

Effect of dimensionality on the electronic structure of Cu, Ag, and Au

Electronic structure and optical properties of rare earth sesquioxides (R2O3, R=La, Pr, and Nd)