Evidence of magnetic ordering in tellurium substituted FeSb2

We report on a⁵⁷Fe Mössbauer study of tellurium substituted FeSb₂, FeSb_2?x Tc _x (x=0.2, 0.4, 0.6), at temperatures between 4.2 K and 300 K. For all three alloys, the Mössbauer spectra at 4.2 K are characteristic of a magnetically ordered state. The hyperfine field at Fe site increases with increasing tellurium concentration. The magnetic character may be attributed to the existence of a very narrow band gap leading to fairly strong Coulomb and exchange interactions between holes in the valence band and electrons in the conduction band.