Narrow D-band Research Articles

Electric and magnetic properties of B2 structure compounds: NiAl, CoAl

Electrical resistivity, thermoelectric power, and magnetic susceptibility or magnetization have been measured at room temperature and below on compositions surrounding NiAl (49–51 at. % Al) and CoAl (42–54% Al). The resistivity-composition plots show a minimum near 50 per cent. The slopes of the ϱ vs. composition plots are markedly different on opposite sides of the minimum. The thermoelectric power is n-type with a distinct shoulder at 50 per cent. NiAl is Pauli paramagnetic for all compositions as is CoAl for Al-rich compositions. Co-rich CoAl is ferromagnetic with the magnetization approaching zero at about 50 per cent. These results are used to suggest a qualitative energy band model. The main features of this model are similar to those of Goodenough, i.e. a broad hybrid s- p band and several narrow d-bands formed from transition metal atomic orbitals.

Electron Microprobe and Optical Absorption Study of Colored Kyanites

The characteristic blue color of the mineral kyanite is shown to be caused by traces of Ti(+++) in the range of a few parts per million. Evidence from the intensity and position of optical absorption bands indicates that the unusually intense color probably arises from electron delocalization into narrow d-bands.