HYPERFINE-STRUCTURE OF BETA-FESI2

The Mossbauer spectrum of beta-FeSi2 consists of four lines originatin g from two quadrupole doublets corresponding to two different local en vironments of iron. Measurements in external magnetic fields, and nume rical analysis support the idea that the first and third lines belong to a doublet. This doublet has a negative quadrupole splitting while t he other two lines form a doublet with a positive quadrupole splining. The model of two doublets and randomness of the electric field gradie nt tensor axes fails at fields larger than about 6 T. The quadrupole s plittings as well as the effective internal field show non-trivial lin ear variation with the intensity of the external magnetic held.