Itinerant-electron metamagnetism of Fe(Si,Ge) with B20-type structure

Electronic structures of Fe ₄ Si _{4 - n} Ge _n (n=0-4) with a cubic B20-type structure are calculated by a self-consistent LMTO method. It is found that these compounds are narrow-gap semiconductors in the non-magnetic state. The band gap is found to decrease with increasing n. For n>=2, however, the metallic state with the magnetic moment of about 1μ _B per Fe is shown to be more stable. It is also shown that the characteristic properties of itinerant-electron metamagnetism, i.e., the first-order transition at the Curie temperature and the field-induced metamagnetic transition, may take place at the boundary between the non-magnetic and magnetic states near n=2.