Mössbauer Spectroscopy and Electrical Conductivity of Fe-Dopedβ-Rhombohedral Boron

Abstract

Iron and/or aluminum are doped toβ-rhombohedral boron, and the electrical conductivity and57Fe Mössbauer effect are measured. The temperature dependence of the electrical conductivity is explained as a variable range hopping type. The conductivity increases with an increase in Fe concentration, but it is insensitive to Al concentration. The Mössbauer spectra measured at room temperature are resolved into three kinds of doublets and a sextet due to ferromagnetic FeB. One doublet,γ0, is attributed to Fe3+ions atA1sites, while the others,γ1andγ2, occur from Fe2+ions atDsites. When Fe and Al atoms are simultaneously doped intoβ-boron, the intensity of theγ0doublet decreases and, hence, those of theγ1andγ2doublets relatively increase. The results shows that Fe atoms are moved from A1sites toDsites by Al atoms. It is proposed that theγ1doublet corresponds to Fe2+(D)–Fe2+(D) and theγ2doublet to Fe2+(D) and that a part of Fe2+(D) is in the magnetic state at 4.2 K.