ROLES OF LIGHT INTERSTITIALS IN MAGNETISM OF FE

We present ab-initio electronic structure calculations for layered (Fe X)(1)-(Fe)(5) (X=B, C, and N) and Fe(4)Z of perovskite structure, wher e Z denotes a hypothetical atom with a nuclear charge Z (5 less than o r equal to Z less than or equal to 8). The calculations show, firstly, that the typical-element atoms enhance the magnetic moments of surrou nding Fe atoms and, second, that chemical bonding between Z and Fe ato ms drastically changes its character when Z increases continuously fro m 5 to 8. The latter, which causes a sudden increase in the magnetizat ion near Z similar or equal to 7, may be important to understand the m agnetism of Fe-N systems in general.