MAGNETIC-PROPERTIES AND GAP FORMATION IN FESI

Magnetisation, magnetic susceptibility, resistivity, optical-reflectiv ity and point-contact tunnelling measurements were used to study an Fe Si single crystal. Magnetisation measurements revealed a ferromagnetic contribution which is more pronounced below 100 K. Magnetic susceptib ility, resistivity, far-infrared and point-contact data are consistent with the characterisation of FeSi as a narrow-gap semiconductor or Ko ndo insulator. Fits to our transport data suggest the formation of a g ap at about E(g) similar to 650 K and a fit to our susceptibility data indicates a gap at about E(g) similar to 1200 K. The point-contact ga p is filled at about 60 K. Optical spectra show a significant reductio n of the low frequency reflectivity below 200 K.