Electronic structure and the metamagnetic transition of FeSi at extremely high magnetic fields

A field-induced moment for the narrow-band-gap semiconductor FeSi with a B2 0-type cubic structure is calculated by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation, by introducing empt y spheres in a unit cell. The fixed-spin-moment calculations give two succe ssive metamagnetic transitions. It is found that the first metamagnetic tra nsition will occur at a magnetic field of about 350 T from the nonmagnetic semiconductor to a metallic ferromagnet with a small moment of about 0.1 mu (B)/Fe. This is consistent with the observed anomaly in the electrical cond uctivity at about 390 T The second metamagnetic transition takes place from the small-moment state to a large-moment one with about 1 mu(B)/Fe at abou t 700 T. The critical field of the first metamagnetic transition is shown t o depend strongly on the value of the band-gap where the Fermi level lies.